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Hebrew calendar

Hebrew calendar

Overview
The Hebrew calendar or Jewish calendar, is a lunisolar calendar
Lunisolar calendar
A lunisolar calendar is a calendar in many cultures whose date indicates both the moon phase and the time of the solar year. If the solar year is defined as a tropical year then a lunisolar calendar will give an indication of the season; if it is taken as a sidereal year then the calendar will...

 used today predominantly for Jewish religious observances. It determines the dates for Jewish holiday
Jewish holiday
Jewish holidays are days observed by Jews as holy or secular commemorations of important events in Jewish history. In Hebrew, Jewish holidays and festivals, depending on their nature, may be called yom tov or chag or ta'anit...

s and the appropriate public reading
Torah reading
Torah reading is a Jewish religious ritual that involves the public reading of a set of passages from a Torah scroll. The term often refers to the entire ceremony of removing the Torah scroll from the ark, chanting the appropriate excerpt with special cantillation, and returning the scroll to...

 of Torah portions, yahrzeits (dates to commemorate the death of a relative), and daily Psalm reading, among many ceremonial uses. In Israel
Israel
The State of Israel is a parliamentary republic located in the Middle East, along the eastern shore of the Mediterranean Sea...

, it is an official calendar for civil purposes and provides a time frame for agriculture.

Originally the Hebrew calendar was used by Jews for all daily purposes, but following the conquest of Jerusalem by Pompey
Pompey
Gnaeus Pompeius Magnus, also known as Pompey or Pompey the Great , was a military and political leader of the late Roman Republic...

 in 63 BCE (see also Iudaea province
Iudaea Province
Judaea or Iudaea are terms used by historians to refer to the Roman province that extended over parts of the former regions of the Hasmonean and Herodian kingdoms of Israel...

), Jews began additionally following the imperial civil calendar
Julian calendar
The Julian calendar began in 45 BC as a reform of the Roman calendar by Julius Caesar. It was chosen after consultation with the astronomer Sosigenes of Alexandria and was probably designed to approximate the tropical year .The Julian calendar has a regular year of 365 days divided into 12 months...

, which was decreed in 45 BCE, for civic matters such as the payment of taxes and dealings with government officials.

The Hebrew calendar has evolved over time.
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Encyclopedia
The Hebrew calendar or Jewish calendar, is a lunisolar calendar
Lunisolar calendar
A lunisolar calendar is a calendar in many cultures whose date indicates both the moon phase and the time of the solar year. If the solar year is defined as a tropical year then a lunisolar calendar will give an indication of the season; if it is taken as a sidereal year then the calendar will...

 used today predominantly for Jewish religious observances. It determines the dates for Jewish holiday
Jewish holiday
Jewish holidays are days observed by Jews as holy or secular commemorations of important events in Jewish history. In Hebrew, Jewish holidays and festivals, depending on their nature, may be called yom tov or chag or ta'anit...

s and the appropriate public reading
Torah reading
Torah reading is a Jewish religious ritual that involves the public reading of a set of passages from a Torah scroll. The term often refers to the entire ceremony of removing the Torah scroll from the ark, chanting the appropriate excerpt with special cantillation, and returning the scroll to...

 of Torah portions, yahrzeits (dates to commemorate the death of a relative), and daily Psalm reading, among many ceremonial uses. In Israel
Israel
The State of Israel is a parliamentary republic located in the Middle East, along the eastern shore of the Mediterranean Sea...

, it is an official calendar for civil purposes and provides a time frame for agriculture.

Originally the Hebrew calendar was used by Jews for all daily purposes, but following the conquest of Jerusalem by Pompey
Pompey
Gnaeus Pompeius Magnus, also known as Pompey or Pompey the Great , was a military and political leader of the late Roman Republic...

 in 63 BCE (see also Iudaea province
Iudaea Province
Judaea or Iudaea are terms used by historians to refer to the Roman province that extended over parts of the former regions of the Hasmonean and Herodian kingdoms of Israel...

), Jews began additionally following the imperial civil calendar
Julian calendar
The Julian calendar began in 45 BC as a reform of the Roman calendar by Julius Caesar. It was chosen after consultation with the astronomer Sosigenes of Alexandria and was probably designed to approximate the tropical year .The Julian calendar has a regular year of 365 days divided into 12 months...

, which was decreed in 45 BCE, for civic matters such as the payment of taxes and dealings with government officials.

The Hebrew calendar has evolved over time. For example, until the Tannaitic period, the months were set by observation of a new crescent moon
Lunar phase
A lunar phase or phase of the moon is the appearance of the illuminated portion of the Moon as seen by an observer, usually on Earth. The lunar phases change cyclically as the Moon orbits the Earth, according to the changing relative positions of the Earth, Moon, and Sun...

, with an additional month added every two or three years to keep Passover in the spring, again based on observation of natural events, namely the ripening of the barley crop, the age of the kids lambs and doves, the ripeness of the fruit trees, and the relation to the Tekufah. Through the Amoraic period and into the Geonic period, this system was displaced by mathematical rules. The principles and rules appear to have been settled by the time Maimonides
Maimonides
Moses ben-Maimon, called Maimonides and also known as Mūsā ibn Maymūn in Arabic, or Rambam , was a preeminent medieval Jewish philosopher and one of the greatest Torah scholars and physicians of the Middle Ages...

 compiled the Mishneh Torah
Mishneh Torah
The Mishneh Torah subtitled Sefer Yad ha-Hazaka is a code of Jewish religious law authored by Maimonides , one of history's foremost rabbis...

in the 12th century.

Because of the roughly eleven-day difference between twelve lunar month
Lunar month
In lunar calendars, a lunar month is the time between two identical syzygies . There are many variations. In Middle-Eastern and European traditions, the month starts when the young crescent moon becomes first visible at evening after conjunction with the Sun one or two days before that evening...

s and one solar year, the length of the Hebrew calendar year varies in the repeating 19-year Metonic cycle
Metonic cycle
In astronomy and calendar studies, the Metonic cycle or Enneadecaeteris is a period of very close to 19 years which is remarkable for being very nearly a common multiple of the solar year and the synodic month...

 of 235 lunar months, with the intercalary month added according to defined rules every two or three years, for a total of 7 times per 19 years. Seasonal references in the Hebrew calendar reflect its development in the region east of the Mediterranean and the times and climate of the Northern Hemisphere
Northern Hemisphere
The Northern Hemisphere is the half of a planet that is north of its equator—the word hemisphere literally means “half sphere”. It is also that half of the celestial sphere north of the celestial equator...

. The Hebrew calendar year is longer by about 6 minutes and 25+25/57 seconds than the present-day mean solar year, so that every 224 years, the Hebrew calendar will fall a full day behind the modern solar year, and about every 231 years it will fall a full day behind the Gregorian calendar year.

The present counting method for years use the Anno Mundi
Anno Mundi
' , abbreviated as AM or A.M., refers to a Calendar era based on the Biblical creation of the world. Numerous efforts have been made to determine the Biblical date of Creation, yielding varying results. Besides differences in interpretation, which version of the Bible is being referenced also...

 epoch
Epoch (reference date)
In the fields of chronology and periodization, an epoch is an instance in time chosen as the origin of a particular era. The "epoch" then serves as a reference point from which time is measured...

 (Latin
Latin
Latin is an Italic language originally spoken in Latium and Ancient Rome. It, along with most European languages, is a descendant of the ancient Proto-Indo-European language. Although it is considered a dead language, a number of scholars and members of the Christian clergy speak it fluently, and...

 for "in the year of the world"), abbreviated AM or A.M. and also referred to as the Hebrew era. Hebrew year 5771 (a leap year
Leap year
A leap year is a year containing one extra day in order to keep the calendar year synchronized with the astronomical or seasonal year...

) began on 9 September 2010 and ended on 28 September 2011. Hebrew year 5772 began at sunset on 28 September 2011 and will end on 16 September 2012.

Structure


The Jewish calendar is a lunisolar calendar
Lunisolar calendar
A lunisolar calendar is a calendar in many cultures whose date indicates both the moon phase and the time of the solar year. If the solar year is defined as a tropical year then a lunisolar calendar will give an indication of the season; if it is taken as a sidereal year then the calendar will...

, or fixed lunar year, based on twelve lunar month
Lunar month
In lunar calendars, a lunar month is the time between two identical syzygies . There are many variations. In Middle-Eastern and European traditions, the month starts when the young crescent moon becomes first visible at evening after conjunction with the Sun one or two days before that evening...

s of twenty-nine or thirty days, with an intercalary lunar month added seven times every nineteen years (once every two to three years) to synchronize the twelve lunar cycles with the slightly longer solar year. Each Jewish lunar month starts with the new moon
New moon
In astronomical terminology, the new moon is the lunar phase that occurs when the Moon, in its monthly orbital motion around Earth, lies between Earth and the Sun, and is therefore in conjunction with the Sun as seen from Earth...

. Although originally the new lunar crescent had to be observed and certified by witnesses, the moment of the new moon is now approximated arithmetically.

Concurrently there is a weekly cycle of seven days, mirroring the seven-day period of the Book of Genesis in which the world is created. The names for the days of the week, like those in the Creation story, are simply the day number
Ordinal number (linguistics)
In linguistics, ordinal numbers are the words representing the rank of a number with respect to some order, in particular order or position . Its use may refer to size, importance, chronology, etc...

 within the week, with Shabbat
Shabbat
Shabbat is the seventh day of the Jewish week and a day of rest in Judaism. Shabbat is observed from a few minutes before sunset on Friday evening until a few minutes after when one would expect to be able to see three stars in the sky on Saturday night. The exact times, therefore, differ from...

 being the seventh day. The Jewish day always runs from sunset to the next sunset; the formal adjustments used to specify a standard time
Standard time
Standard time is the result of synchronizing clocks in different geographical locations within a time zone to the same time rather than using the local meridian as in local mean time or solar time. Historically, this helped in the process of weather forecasting and train travel. The concept...

 and time zone
Time zone
A time zone is a region on Earth that has a uniform standard time for legal, commercial, and social purposes. In order for the same clock time to always correspond to the same portion of the day as the Earth rotates , different places on the Earth need to have different clock times...

s are not relevant to the Jewish calendar.

The twelve regular months are: Nisan
Nisan
Nisan is the first month of the ecclesiastical year and the seventh month of the civil year, on the Hebrew calendar. The name of the month is Babylonian; in the Torah it is called the month of the Aviv, referring to the month in which barley was ripe. It is a spring month of 30 days...

 (30 days), Iyar
Iyar
Iyar is the eighth month of the civil year and the second month of the ecclesiastical year on the Hebrew calendar. The name is Babylonian in origin. It is a spring month of 29 days. Iyar usually falls in April–June on the Gregorian calendar.In the Hebrew Bible, before the Babylonian Exile, the...

 (29 days), Sivan
Sivan
Sivan is the ninth month of the civil year and the third month of the ecclesiastical year on the Hebrew calendar. It is a spring month of 30 days...

 (30 days), Tammuz (29 days), Av (30 days), Elul
Elul
Elul is the twelfth month of the Jewish civil year and the sixth month of the ecclesiastical year on the Hebrew calendar. It is a summer month of 29 days...

 (29 days), Tishrei
Tishrei
Tishrei or Tishri , Tiberian: ; from Akkadian "Beginning", from "To begin") is the first month of the civil year and the seventh month of the ecclesiastical year in the Hebrew calendar. The name of the month is Babylonian. It is an autumn month of 30 days...

  (30 days), Marcheshvan (29 or 30 days), Kislev
Kislev
Kislev Kislev Tiberian ; also Chislev is the third month of the civil year and the ninth month of the ecclesiastical year on the Hebrew calendar....

 (29 or 30 days), Tevet
Tevet
Tebet is the fourth month of the civil year and the tenth month of the ecclesiastical year on the Hebrew calendar. It follows Kislev and precedes Shevat. It is a winter month of 29 days...

 (29 days), Shevat
Shevat
Shevat is the fifth month of the civil year and the eleventh month of the ecclesiastical year on the Hebrew calendar. It is a winter month of 30 days...

 (30 days), and Adar
Adar
Adar is the sixth month of the civil year and the twelfth month of the ecclesiastical year on the Hebrew calendar. It is a winter month of 29 days...

 (29 days). In the leap years (such as 5771) an additional month, Adar I (30 days) is added after Shevat, and the regular Adar is referred to as "Adar II".

The first month of the festival year is Nisan. 15 Nisan is the start of the festival of Pesach
Passover
Passover is a Jewish holiday and festival. It commemorates the story of the Exodus, in which the ancient Israelites were freed from slavery in Egypt...

, corresponding to the full moon
Full moon
Full moon lunar phase that occurs when the Moon is on the opposite side of the Earth from the Sun. More precisely, a full moon occurs when the geocentric apparent longitudes of the Sun and Moon differ by 180 degrees; the Moon is then in opposition with the Sun.Lunar eclipses can only occur at...

 of Nisan. Pesach is a spring festival associated with the barley harvest, so the leap-month mentioned above is intercalated periodically to keep this festival in the northern hemisphere's spring season. Since the adoption of a fixed calendar, intercalations in the Hebrew calendar have been at fixed points in a 19-year cycle. Prior to this, the intercalation was determined empirically:

The year may be intercalated on three grounds: 'aviv [i.e.the ripeness of barley], fruits of trees, and the equinox. On two of these grounds it should be intercalated, but not on one of them alone.


The Bible designates Nisan, which it calls Aviv , as the first month of the year . At the same time, the season of the fall Festival of Booths (Sukkoth), is called "the end of the year" . The Sabbatical year in which the land was to lie fallow, necessarily began at the time the winter barley and winter wheat would have been sown, in the fall. The Gezer calendar
Gezer calendar
The Gezer calendar is a tablet of soft limestone inscription, dating to the 10th century BCE. Scholars are divided as to whether the script and language are Phoenician or paleo-Hebrew, which were linguistically very similar in this period....

, an Israelite or Canaanite inscription c. 900 BCE, also begins in the fall.

Modern practice follows the scheme described in the Mishnah: Nisan is the new year for the reigns of kings and the festivals. Rosh Hashanah
Rosh Hashanah
Rosh Hashanah , , is the Jewish New Year. It is the first of the High Holy Days or Yamim Nora'im which occur in the autumn...

, which means "the head of the year", and is celebrated in the month of Tishrei
Tishrei
Tishrei or Tishri , Tiberian: ; from Akkadian "Beginning", from "To begin") is the first month of the civil year and the seventh month of the ecclesiastical year in the Hebrew calendar. The name of the month is Babylonian. It is an autumn month of 30 days...

, is "the new year for the counting of years." This is when the numbered year changes, which is most significant for determining the Shemittah and Yovel years.

Sources and history


The Tanakh
Tanakh
The Tanakh is a name used in Judaism for the canon of the Hebrew Bible. The Tanakh is also known as the Masoretic Text or the Miqra. The name is an acronym formed from the initial Hebrew letters of the Masoretic Text's three traditional subdivisions: The Torah , Nevi'im and Ketuvim —hence...

 contains several commandments
613 mitzvot
The 613 commandments is a numbering of the statements and principles of law, ethics, and spiritual practice contained in the Torah or Five Books of Moses...

 related to the keeping of the calendar and the lunar cycle, and records changes that have taken place to the Hebrew calendar.

Day

For smaller units of time, see Measurement of hours below.

The Jewish day is of no fixed length. The Jewish day is modeled on the reference to "...there was evening and there was morning..." in the Creation story in the first chapter of Genesis. Accordingly, it runs from sunset (start of "the evening") to the next sunset. However, some apply special rules at very high latitudes when the sun remains above or below the horizon for longer than a civil day.

There is no clock in the Jewish scheme, so that a civil clock is used. Though the civil clock incorporates local adoptions of various conventions such as time zone
Time zone
A time zone is a region on Earth that has a uniform standard time for legal, commercial, and social purposes. In order for the same clock time to always correspond to the same portion of the day as the Earth rotates , different places on the Earth need to have different clock times...

s, standard time
Standard time
Standard time is the result of synchronizing clocks in different geographical locations within a time zone to the same time rather than using the local meridian as in local mean time or solar time. Historically, this helped in the process of weather forecasting and train travel. The concept...

s and daylight saving, these have no place in the Jewish scheme. The civil clock is used only as a reference point - in expressions such as: "Shabbat starts at ...". The steady progression of sunset around the world and seasonal changes results in gradual civil time changes from one day to the next based on observable astronomical phenomena (the sunset) and not on man-made laws and conventions.

Instead of the international date line
International Date Line
The International Date Line is a generally north-south imaginary line on the surface of the Earth, passing through the middle of the Pacific Ocean, that designates the place where each calendar day begins...

 convention, there are varying opinions as to where the day changes. One opinion uses the antimeridian of Jerusalem. (Jerusalem is 35°13’ east of the prime meridian
Prime Meridian
The Prime Meridian is the meridian at which the longitude is defined to be 0°.The Prime Meridian and its opposite the 180th meridian , which the International Date Line generally follows, form a great circle that divides the Earth into the Eastern and Western Hemispheres.An international...

, so the antimeridian is at 144°47' W, passing through eastern Alaska
Alaska
Alaska is the largest state in the United States by area. It is situated in the northwest extremity of the North American continent, with Canada to the east, the Arctic Ocean to the north, and the Pacific Ocean to the west and south, with Russia further west across the Bering Strait...

.) Other opinions exist as well.

Weeks



The Hebrew calendar follows a seven-day weekly cycle, which runs concurrently but independently of the monthly and annual cycles. The names for the days of the week are simply the day number within the week. In Hebrew, these names may be abbreviated using the numerical value
Hebrew numerals
The system of Hebrew numerals is a quasi-decimal alphabetic numeral system using the letters of the Hebrew alphabet.In this system, there is no notation for zero, and the numeric values for individual letters are added together...

 of the Hebrew letters, for example (Day 1, or Yom Rishon ):
  1. Yom Rishon - (abbreviated ) = "first day" = Sunday (starting at preceding sunset)
  2. Yom Sheni - (abbr. ) = "second day" = Monday
  3. Yom Shlishi - (abbr. ) = "third day" = Tuesday
  4. Yom Reviʻi - (abbr. ) = "fourth day" = Wednesday
  5. Yom Chamishi - (abbr. ) = "fifth day" = Thursday
  6. Yom Shishi - (abbr. ) = "sixth day" = Friday
  7. Yom Shabbat - (abbr. ) or more usually - Shabbat = "Sabbath day (Rest day)" = Saturday


The names of the days of the week are modeled on the seven days mentioned in the Creation story. For example, "... And there was evening and there was morning, one day". One day also translates to first day or day one. Similarly, see , , , , and .

The Jewish Shabbat
Shabbat
Shabbat is the seventh day of the Jewish week and a day of rest in Judaism. Shabbat is observed from a few minutes before sunset on Friday evening until a few minutes after when one would expect to be able to see three stars in the sky on Saturday night. The exact times, therefore, differ from...

 has a special role in the Jewish weekly cycle. There are many special rules which relate to the Shabbat, discussed more fully in the Talmudic tractate Shabbat
Shabbat (Talmud)
Shabbat is first tractate in the Order of Moed, of the Mishnah and Talmud. The tractate consists of 24 chapters.The tractate primarily deals with laws relating to Shabbat , and the activities prohibited on Shabbat and distinguishes between Biblical prohibitions and Rabbinic prohibitions...

.

In Hebrew, the word Shabbat can also mean "(Talmudic) week", so that in ritual liturgy a phrase like "Yom Reviʻi bəShabbat" means "the fourth day in the week".

Importance of lunar months


From very early times, the Mesopotamia
Mesopotamia
Mesopotamia is a toponym for the area of the Tigris–Euphrates river system, largely corresponding to modern-day Iraq, northeastern Syria, southeastern Turkey and southwestern Iran.Widely considered to be the cradle of civilization, Bronze Age Mesopotamia included Sumer and the...

n lunisolar calendar
Lunisolar calendar
A lunisolar calendar is a calendar in many cultures whose date indicates both the moon phase and the time of the solar year. If the solar year is defined as a tropical year then a lunisolar calendar will give an indication of the season; if it is taken as a sidereal year then the calendar will...

 was in wide use by the countries of the western Asia region. The structure, which was also used by the Israelites, was based on lunar months with the intercalation of an additional month to bring the cycle closer to the solar cycle.

stresses the importance in Israelite religious observance of the new month (Hebrew: , Rosh Chodesh
Rosh Chodesh
Rosh Chodesh or Rosh ḥodesh is the name for the first day of every month in the Hebrew calendar, marked by the appearance of the new moon. The new moon is marked by the day and hour that the new crescent is observed...

, "beginning of the month"): "... in your new moons, ye shall blow with the trumpets over your burnt-offerings..." Similarly in . "The beginning of the month" meant the appearance of a new moon
New moon
In astronomical terminology, the new moon is the lunar phase that occurs when the Moon, in its monthly orbital motion around Earth, lies between Earth and the Sun, and is therefore in conjunction with the Sun as seen from Earth...

. In prophet Amos, the new moon seem to be described simply as Kadosh
Kadosh
Kadosh is a 1999 film by Israeli director Amos Gitai. It was entered into the 1999 Cannes Film Festival.-Plot:Kadosh is a bleak drama about the plight of women in Haredi society. In the opening scene, Meir , a young Talmudic scholar, thanks God in his morning prayers for not being born a woman...

.

According to the Mishnah
Mishnah
The Mishnah or Mishna is the first major written redaction of the Jewish oral traditions called the "Oral Torah". It is also the first major work of Rabbinic Judaism. It was redacted c...

and Tosefta
Tosefta
The Tosefta is a compilation of the Jewish oral law from the period of the Mishnah.-Overview:...

, in the Maccabean, Herodian, and Mishnaic periods, new months were determined by the sighting of a new crescent, with two eye witnesses required to testify to the Sanhedrin
Sanhedrin
The Sanhedrin was an assembly of twenty-three judges appointed in every city in the Biblical Land of Israel.The Great Sanhedrin was the supreme court of ancient Israel made of 71 members...

 to having seen the new lunar crescent at sunset. The practice in the time of Gamaliel II
Gamaliel II
Rabban Gamaliel II was the first person to lead the Sanhedrin as Nasi after the fall of the second temple, which occurred in 70 CE. Gamliel was appointed nasi approximately 10 years later. Gamaliel II was the son of Shimon ben Gamaliel, one of Jerusalem's foremost men in the war against the...

 (c. 100 CE) was for witnesses to select the appearance of the moon from a collection of drawings that depicted the crescent in a variety of orientations, only a few of which could be valid in any given month. These observations were compared against calculations. When thirty days elapsed since the last new moon, the witnesses were readily believed.

At first the beginning of each Jewish month was signaled to the communities of Israel and beyond by fires lit on mountaintops, but after the Samaritan
Samaritan
The Samaritans are an ethnoreligious group of the Levant. Religiously, they are the adherents to Samaritanism, an Abrahamic religion closely related to Judaism...

s began to light false fires, messengers were sent. The inability of the messengers to reach communities outside Israel before mid-month High Holy Days (Succot and Passover
Passover
Passover is a Jewish holiday and festival. It commemorates the story of the Exodus, in which the ancient Israelites were freed from slavery in Egypt...

) led outlying communities to celebrate scriptural festivals for two days rather than one, observing the second feast-day of the Jewish diaspora
Jewish diaspora
The Jewish diaspora is the English term used to describe the Galut גלות , or 'exile', of the Jews from the region of the Kingdom of Judah and Roman Iudaea and later emigration from wider Eretz Israel....

 because of uncertainty of whether the previous month ended after 29 or 30 days.

In his work Mishneh Torah
Mishneh Torah
The Mishneh Torah subtitled Sefer Yad ha-Hazaka is a code of Jewish religious law authored by Maimonides , one of history's foremost rabbis...

(1178), Maimonides included a chapter "Sanctification of the New Moon", in which he discusses the calendrical rules and their scriptural basis. He notes,
"By how much does the solar year exceed the lunar year? By approximately 11 days. Therefore, whenever this excess accumulates to about 30 days, or a little more or less, one month is added and the particular year is made to consist of 13 months, and this is the so-called embolismic (intercalated) year. For the year could not consist of twelve months plus so-and-so many days, since it is said: throughout the months of the year , which implies that we should count the year by months and not by days."

Names of months


Biblical references to the pre-Jewish calendar include ten months identified by number rather than by name. In parts of the Torah portion Noach (Noah) (specifically, , ) it is implied that the months are thirty days long. There is also indication that there were twelve months in the annual cycle .

Many countries in the western Asian region used the Mesopotamian calendar from very early times, though the names of months varied. Prior to the Babylonian exile, the names of only four months are referred to in the Tanakh
Tanakh
The Tanakh is a name used in Judaism for the canon of the Hebrew Bible. The Tanakh is also known as the Masoretic Text or the Miqra. The name is an acronym formed from the initial Hebrew letters of the Masoretic Text's three traditional subdivisions: The Torah , Nevi'im and Ketuvim —hence...

:
  • Aviv - first month - literally "spring" ;
  • Ziv
    Iyar
    Iyar is the eighth month of the civil year and the second month of the ecclesiastical year on the Hebrew calendar. The name is Babylonian in origin. It is a spring month of 29 days. Iyar usually falls in April–June on the Gregorian calendar.In the Hebrew Bible, before the Babylonian Exile, the...

    - second month - literally "light" ;
  • Ethanim - seventh month - literally "strong" in plural, perhaps referring to strong rains ; and
  • Bul - eighth month .

All of these are believed to be Canaan
Canaan
Canaan is a historical region roughly corresponding to modern-day Israel, Palestine, Lebanon, and the western parts of Jordan...

ite names, and at least two are Phoenicia
Phoenicia
Phoenicia , was an ancient civilization in Canaan which covered most of the western, coastal part of the Fertile Crescent. Several major Phoenician cities were built on the coastline of the Mediterranean. It was an enterprising maritime trading culture that spread across the Mediterranean from 1550...

n (Northern Canaanite).

During the Babylonian exile, which started in 586 BCE, Babylonian month names
Babylonian calendar
The Babylonian calendar was a lunisolar calendar with years consisting of 12 lunar months, each beginning when a new crescent moon was first sighted low on the western horizon at sunset, plus an intercalary month inserted as needed by decree. The calendar is based on a Sumerian precedecessor...

 were adopted, which are still in use. The Syrian calendar used in the Levant
Levant
The Levant or ) is the geographic region and culture zone of the "eastern Mediterranean littoral between Anatolia and Egypt" . The Levant includes most of modern Lebanon, Syria, Jordan, Israel, the Palestinian territories, and sometimes parts of Turkey and Iraq, and corresponds roughly to the...

 region shares many of the names for months as the Hebrew calendar, such as Nisan, Iyyar, Tammuz, Ab, Elul, Tishri, and Adar, indicating a common Babylonian origin.

Hebrew names and romanized transliteration may somewhat differ, as they do for חשוון / Marcheshvan or כסלו / Kislev: the Hebrew words shown here are those commonly indicated e.g. in newspapers.
In a regular (kesidran) year, Marcheshvan has 29 days and Kislev has 30 days. However, because of the Rosh Hashanah postponement rules (see below) Kislev may lose a day to have 29 days, and the year is called a short (chaser) year, or Marcheshvan may acquire an additional day to have 30 days, and the year is called a full (maleh) year. The calendar rules have been designed to ensure that Rosh Hashanah does not fall on a Sunday, Wednesday or Friday. This is to ensure that Yom Kippur
Yom Kippur
Yom Kippur , also known as Day of Atonement, is the holiest and most solemn day of the year for the Jews. Its central themes are atonement and repentance. Jews traditionally observe this holy day with a 25-hour period of fasting and intensive prayer, often spending most of the day in synagogue...

 does not directly precede or follow Shabbat
Shabbat
Shabbat is the seventh day of the Jewish week and a day of rest in Judaism. Shabbat is observed from a few minutes before sunset on Friday evening until a few minutes after when one would expect to be able to see three stars in the sky on Saturday night. The exact times, therefore, differ from...

, which would create practical difficulties, and that Hoshana Rabbah is not on a Shabbat, in which case certain ceremonies would be lost for a year.

Leap months


The solar year is about eleven days longer than twelve lunar months. The Bible does not directly mention the addition of "embolismic" or intercalary month
Intercalation
Intercalation is the insertion of a leap day, week or month into some calendar years to make the calendar follow the seasons or moon phases. Lunisolar calendars may require intercalations of both days and months.- Solar calendars :...

s. However, without the insertion of embolismic months, Jewish festivals would gradually shift outside of the season
Season
A season is a division of the year, marked by changes in weather, ecology, and hours of daylight.Seasons result from the yearly revolution of the Earth around the Sun and the tilt of the Earth's axis relative to the plane of revolution...

s required by the Torah. This has been ruled as implying a requirement for the insertion of embolismic months to reconcile the lunar cycles to the seasons, which are integral to solar yearly cycles.

When the observational form of the calendar was in use, whether or not an embolismic month was announced after the "last month" (Adar
Adar
Adar is the sixth month of the civil year and the twelfth month of the ecclesiastical year on the Hebrew calendar. It is a winter month of 29 days...

) depended on 'aviv [i.e.the ripeness of barley], fruits of trees, and the equinox. On two of these grounds it should be intercalated, but not on one of them alone. It may be noted that in the Bible the name of the first month, Aviv
Nisan
Nisan is the first month of the ecclesiastical year and the seventh month of the civil year, on the Hebrew calendar. The name of the month is Babylonian; in the Torah it is called the month of the Aviv, referring to the month in which barley was ripe. It is a spring month of 30 days...

, literally means "spring". Thus, if Adar was over and Spring had not yet arrived, an additional month was observed. However, according to some traditions, the announcement of the month of Aviv
Nisan
Nisan is the first month of the ecclesiastical year and the seventh month of the civil year, on the Hebrew calendar. The name of the month is Babylonian; in the Torah it is called the month of the Aviv, referring to the month in which barley was ripe. It is a spring month of 30 days...

could also be postponed depending on the condition of roads used by families to come to Jerusalem for Passover
Passover
Passover is a Jewish holiday and festival. It commemorates the story of the Exodus, in which the ancient Israelites were freed from slavery in Egypt...

, adequate numbers of lambs to be sacrificed at the Temple, and on the ripeness of the barley
Barley
Barley is a major cereal grain, a member of the grass family. It serves as a major animal fodder, as a base malt for beer and certain distilled beverages, and as a component of various health foods...

 that was needed for the first fruits ceremony.

Under the codified rules, the Jewish calendar is based on the Metonic cycle
Metonic cycle
In astronomy and calendar studies, the Metonic cycle or Enneadecaeteris is a period of very close to 19 years which is remarkable for being very nearly a common multiple of the solar year and the synodic month...

 of 19 years, of which 12 are common years (12 months) and 7 leap years (13 months). The leap years are years 3, 6, 8, 11, 14, 17, and 19 of the Metonic cycle. Year 19 (there is no year 0) of the Metonic cycle is a year exactly divisible by 19 (when the Jewish year number, when divided by 19, has no remainder). In the same manner, the remainder of the division indicates the year in the Metonic cycle (years 1 to 18) the year is in.

During leap year
Leap year
A leap year is a year containing one extra day in order to keep the calendar year synchronized with the astronomical or seasonal year...

s Adar I (or Adar Aleph — "first Adar") is added before the regular Adar
Adar
Adar is the sixth month of the civil year and the twelfth month of the ecclesiastical year on the Hebrew calendar. It is a winter month of 29 days...

. Adar I is actually considered to be the extra month, and has 30 days. Adar II (or Adar Bet
Bet (letter)
Bet, Beth, Beh, or Vet is the second letter of many Semitic abjads, including Arabic alphabet , Aramaic, Hebrew , Phoenician and Syriac...

 — "second Adar") is the "real" Adar, and has the usual 29 days. For this reason, holidays such as Purim
Purim
Purim is a Jewish holiday that commemorates the deliverance of the Jewish people in the ancient Persian Empire from destruction in the wake of a plot by Haman, a story recorded in the Biblical Book of Esther .Purim is celebrated annually according to the Hebrew calendar on the 14th...

 are observed in Adar II, not Adar I.

New year


and set Aviv (now Nisan
Nisan
Nisan is the first month of the ecclesiastical year and the seventh month of the civil year, on the Hebrew calendar. The name of the month is Babylonian; in the Torah it is called the month of the Aviv, referring to the month in which barley was ripe. It is a spring month of 30 days...

) as "the first of months":
this month shall be unto you the beginning of months; it shall be the first month of the year to you.


Nisan 1 is referred to as the ecclesiastical new year.

In ancient Israel, the start of the ecclesiastical new year for the counting of months and festivals (i.e. Nisan) was determined by reference to Passover
Passover
Passover is a Jewish holiday and festival. It commemorates the story of the Exodus, in which the ancient Israelites were freed from slavery in Egypt...

. Passover begins on 14 Nisan, which corresponds to the full moon
Full moon
Full moon lunar phase that occurs when the Moon is on the opposite side of the Earth from the Sun. More precisely, a full moon occurs when the geocentric apparent longitudes of the Sun and Moon differ by 180 degrees; the Moon is then in opposition with the Sun.Lunar eclipses can only occur at...

 of Nisan. As Passover is a spring festival, 14 Nisan begins on the night of a full moon after the vernal equinox. According to normative Judaism, the verses in require that the months be determined by a proper court with the necessary authority to sanctify the months.

According to some Christians and Karaites, the tradition in ancient Israel was that 1 Nisan would not start until the barley is ripe, being the test for the onset of spring. If the barley was not ripe an intercalary month
Intercalation
Intercalation is the insertion of a leap day, week or month into some calendar years to make the calendar follow the seasons or moon phases. Lunisolar calendars may require intercalations of both days and months.- Solar calendars :...

 would be added before Nisan.

The day most commonly referred to as the "New Year" is 1 Tishrei, which actually begins in the seventh month of the ecclesiastical year. On that day the formal New Year for the counting of years (such as Shmita and Yovel
Jubilee (Biblical)
The Jubilee year is the year at the end of seven cycles of Sabbatical years , and according to Biblical regulations had a special impact on the ownership and management of land in the territory of the kingdoms of Israel and of Judah; there is some debate whether it was the 49th year The Jubilee...

), Rosh Hashanah
Rosh Hashanah
Rosh Hashanah , , is the Jewish New Year. It is the first of the High Holy Days or Yamim Nora'im which occur in the autumn...

 ("head of the year") is observed. (see , which uses the phrase "beginning of the year".) This is the civil new year, and the date on which the year number advances. Certain agricultural practices are also marked from this date.

Josephus
Josephus
Titus Flavius Josephus , also called Joseph ben Matityahu , was a 1st-century Romano-Jewish historian and hagiographer of priestly and royal ancestry who recorded Jewish history, with special emphasis on the 1st century AD and the First Jewish–Roman War, which resulted in the Destruction of...

, in the 1st century CE, states that while -

Moses...appointed Nisan...as the first month for the festivals...the commencement of the year for everything relating to divine worship, but for selling and buying and other ordinary affairs he preserved the ancient order [i. e. the year beginning with Tishrei]."


Edwin Thiele has concluded that the ancient northern Kingdom of Israel counted years using the ecclesiastical new year starting on 1 Aviv (Nisan), while the southern Kingdom of Judah
Kingdom of Judah
The Kingdom of Judah was a Jewish state established in the Southern Levant during the Iron Age. It is often referred to as the "Southern Kingdom" to distinguish it from the northern Kingdom of Israel....

 counted years using the civil new year starting on 1 Tishrei. The practice of the Kingdom of Israel was also that of Babylon
Babylonian calendar
The Babylonian calendar was a lunisolar calendar with years consisting of 12 lunar months, each beginning when a new crescent moon was first sighted low on the western horizon at sunset, plus an intercalary month inserted as needed by decree. The calendar is based on a Sumerian precedecessor...

, as well as other countries of the region. The practice of Judah is still followed.

In fact the Jewish calendar has a multiplicity of new years for different purposes. The use of these dates has been in use for a long time. The use of multiple starting dates for a year is comparable to different starting dates for civil "calendar years", "tax or fiscal years", "academic years", "religious cycles", etc. By the time of the redaction of the Mishnah
Mishnah
The Mishnah or Mishna is the first major written redaction of the Jewish oral traditions called the "Oral Torah". It is also the first major work of Rabbinic Judaism. It was redacted c...

, Rosh Hashanah 1:1 (c. 200 CE), jurists had identified four new-year dates:

The 1st of Nisan is the new year for kings and feasts; the 1st of Elul is the new year for the tithe of cattle... the 1st of Tishri is the new year for years, of the years of release and jubilee years
Jubilee (Biblical)
The Jubilee year is the year at the end of seven cycles of Sabbatical years , and according to Biblical regulations had a special impact on the ownership and management of land in the territory of the kingdoms of Israel and of Judah; there is some debate whether it was the 49th year The Jubilee...

, for the planting and for vegetables; and the 1st of Shevat is the new year for trees-so the school of Shammai; and the school of Hillel say: On the 15th thereof.


The month of Elul
Elul
Elul is the twelfth month of the Jewish civil year and the sixth month of the ecclesiastical year on the Hebrew calendar. It is a summer month of 29 days...

 is the new year for counting animal tithes (ma'aser). Tu Bishvat
Tu Bishvat
Tu Bishvat or Tu B'Shevat is a minor Jewish holiday, occurring on the 15th day of the Hebrew month of Shevat . It is also called "The New Year of the Trees" or...

("the 15th of Shevat
Shevat
Shevat is the fifth month of the civil year and the eleventh month of the ecclesiastical year on the Hebrew calendar. It is a winter month of 30 days...

") marks the new year for trees (and agricultural tithes).

Epoch


Since about the 3rd century CE, the Jewish calendar has used the Anno Mundi
Anno Mundi
' , abbreviated as AM or A.M., refers to a Calendar era based on the Biblical creation of the world. Numerous efforts have been made to determine the Biblical date of Creation, yielding varying results. Besides differences in interpretation, which version of the Bible is being referenced also...

 epoch
Epoch (reference date)
In the fields of chronology and periodization, an epoch is an instance in time chosen as the origin of a particular era. The "epoch" then serves as a reference point from which time is measured...

 (Latin
Latin
Latin is an Italic language originally spoken in Latium and Ancient Rome. It, along with most European languages, is a descendant of the ancient Proto-Indo-European language. Although it is considered a dead language, a number of scholars and members of the Christian clergy speak it fluently, and...

 for “in the year of the world,” abbreviated AM or A.M.; Hebrew ), sometimes referred to as the “Hebrew era.” According to Rabbinic reckoning, the beginning of "year 1" is not Creation
Creation according to Genesis
The Genesis creation narrative describes the divine creation of the world including the first man and woman...

, but about one year before Creation, with the new moon of its first month (Tishrei) to be called molad tohu (the mean new moon of chaos or nothing).

The Jewish calendar's epoch (reference date), 1 Tishrei 1 AM, is equivalent to Monday, 7 October 3761 BCE in the proleptic Julian calendar
Proleptic Julian calendar
The proleptic Julian calendar is produced by extending the Julian calendar to dates preceding AD 4 when its quadrennial leap year stabilized. The leap years actually observed between its official implementation in 45 BC and AD 4 were erratic, see the Julian calendar article for details.A calendar...

, the equivalent tabular date (same daylight period) and is about one year before the traditional Jewish date of Creation
Dating Creation
Cultures throughout history have attempted to date the beginning of the the world in the past, so methods of dating Creation have involved analysing scriptures or ancient texts.-Ancient creation dates:...

 on 25 Elul AM 1, based upon the Seder Olam Rabbah
Seder Olam Rabbah
Seder Olam Rabbah is a 2nd century CE Hebrew language chronology detailing the dates of biblical events from the Creation to Alexander the Great's conquest of Persia...

of Rabbi Yossi ben Halafta, a 2nd century CE sage. Thus, adding 3760 before Rosh Hashanah
Rosh Hashanah
Rosh Hashanah , , is the Jewish New Year. It is the first of the High Holy Days or Yamim Nora'im which occur in the autumn...

 or 3761 after to a Julian or Gregorian year number after 1 CE will yield the Hebrew year. For earlier years there may be a discrepancy (see: Missing years (Jewish calendar)).

The Jewish year 5771 AM began on 9 September 2010 (1 Tishrei or Rosh Hashanah) and, since it is a 13-month year, ended on 28 September 2011 (29 Elul).

In Hebrew there are 2 common ways of writing the year number: 1. with the thousands, called ("major era"). 2. without the thousands, called ("minor era").

Other systems


The Seder Olam Rabbah
Seder Olam Rabbah
Seder Olam Rabbah is a 2nd century CE Hebrew language chronology detailing the dates of biblical events from the Creation to Alexander the Great's conquest of Persia...

also recognized the importance of the Jubilee
Jubilee (Biblical)
The Jubilee year is the year at the end of seven cycles of Sabbatical years , and according to Biblical regulations had a special impact on the ownership and management of land in the territory of the kingdoms of Israel and of Judah; there is some debate whether it was the 49th year The Jubilee...

 and Sabbatical cycles as a long-term calendrical system, and attempted at various places to fit the Sabbatical and Jubilee years into its chronological scheme.

Before the adoption of the current year numbering system, other systems were in use. In early times, the years were counted from some significant historic event. (e.g. ) During the period of the monarchy, it was the widespread practice in western Asia to use era year numbers according to the accession year of the monarch of the country involved. This practice was also followed by the united kingdom of Israel (e.g. ), kingdom of Judah (e.g. ), kingdom of Israel (e.g. ), Persia (e.g. ) and others. Besides, the author of Kings coordinated dates in the two kingdoms by giving the accession year of a monarch in terms of the year of the monarch of the other kingdom, (e.g. ) though some commentators note that these dates do not synchronise. Other era dating systems have been used at other times. For example, during the Babylonian captivity, Ezekiel
Ezekiel
Ezekiel , "God will strengthen" , is the central protagonist of the Book of Ezekiel in the Hebrew Bible. In Judaism, Christianity and Islam, Ezekiel is acknowledged as a Hebrew prophet...

 counted the years from the first deportation, that of Jehoiachin, (e.g. ). The era year was then called "year of the captivity of Jehoiachin". (e.g. )
During the Greek period, Seleucid era
Seleucid era
The Seleucid era was a system of numbering years in use by the Seleucid Empire and other countries among the ancient Hellenistic civilizations. The era dates from the return of Seleucus I Nicator to Babylon in 311 BC after his exile in Ptolemaic Egypt, considered by Seleucus and his court to mark...

 counting was used. (e.g. 1 Maccabees 1:54)

Karaite calendar


For several centuries, many Karaite Jews, especially those outside Israel, followed the calculated Rabbinic calendar, because it was not possible during the exile to retrieve accurate new moon sightings, and aviv barley data from the land of Israel, which had to be relayed to the entire Karaite Jewish community. However, since the establishment of the State of Israel, and especially since the Six Day War, most Karaite Jews have made aliyah
Aliyah
Aliyah is the immigration of Jews to the Land of Israel . It is a basic tenet of Zionist ideology. The opposite action, emigration from Israel, is referred to as yerida . The return to the Holy Land has been a Jewish aspiration since the Babylonian exile...

, and can now again use the observational calendar.

Karaites use the lunar month and the solar year, but the Karaite calendar differs from the Rabbinic calendar in a number of ways.

For Karaites, the beginning of each month, the Rosh Chodesh
Rosh Chodesh
Rosh Chodesh or Rosh ḥodesh is the name for the first day of every month in the Hebrew calendar, marked by the appearance of the new moon. The new moon is marked by the day and hour that the new crescent is observed...

, can be calculated, but is confirmed by the observation in Israel
Israel
The State of Israel is a parliamentary republic located in the Middle East, along the eastern shore of the Mediterranean Sea...

 of the first sightings of the new moon. This may result in an occasional variation of a maximum of one day, depending on the inability to observe the new moon. The day is usually "picked up" in the next month.

The addition of the leap month (Adar II) is determined by observing in Israel the ripening of barley at a specific stage (defined by Karaite tradition) (called aviv), rather than using the calculated and fixed calendar of Rabbinic Judaism
Rabbinic Judaism
Rabbinic Judaism or Rabbinism has been the mainstream form of Judaism since the 6th century CE, after the codification of the Talmud...

. Occasionally this results in Karaites being one month ahead of other Jews using the calculated Rabbinic calendar. The "lost" month would be "picked up" in the next cycle when Karaites would observe a leap month while other Jews would not.

Furthermore, the seasonal drift of the Rabbinic calendar is avoided, resulting in the years affected by the drift starting one month earlier in the Karaite calendar.

Also, the four rules of postponement of the Rabbinic calendar are not applied, as they are not mentioned in the Tanakh
Tanakh
The Tanakh is a name used in Judaism for the canon of the Hebrew Bible. The Tanakh is also known as the Masoretic Text or the Miqra. The name is an acronym formed from the initial Hebrew letters of the Masoretic Text's three traditional subdivisions: The Torah , Nevi'im and Ketuvim —hence...

. This can affect the dates observed for all the Jewish holidays in a particular year by one day.

Observational principles



Evaluation of the Mishnaic evidence


It has been noted that the procedures described in the Mishnah and Tosefta are all plausible procedures for regulating an empirical lunar calendar. Fire-signals, for example, or smoke-signals, are known from the pre-exilic Lachish ostraca. Furthermore, the Mishnah contains laws that reflect the uncertainties of an empirical calendar. Mishnah Sanhedrin, for example, holds that when one witness holds that an event took place on a certain day of the month, and another that the same event took place on the following day, their testimony can be held to agree, since the length of the preceding month was uncertain. Another Mishnah takes it for granted that it cannot be known in advance whether a year's lease is for twelve or thirteen months. Hence it is a reasonable conclusion that the Mishnaic calendar was actually used in the Mishnaic period.

The accuracy of the Mishnah's claim that the Mishnaic calendar was also used in the late Second Temple period is less certain. One scholar has noted that there are no laws from Second Temple period sources that indicate any doubts about the length of a month or of a year. This led him to propose that the priests must have had some form of computed calendar or calendrical rules that allowed them to know in advance whether a month would have 30 or 29 days, and whether a year would have 12 or 13 months.

Modern calendar


Between 70 CE and 1178 CE, the observation-based calendar was gradually replaced by a mathematically calculated one. Except for the epoch year number, the calendar rules reached their current form by the beginning of the 9th century, as described by the Muslim
Muslim
A Muslim, also spelled Moslem, is an adherent of Islam, a monotheistic, Abrahamic religion based on the Quran, which Muslims consider the verbatim word of God as revealed to prophet Muhammad. "Muslim" is the Arabic term for "submitter" .Muslims believe that God is one and incomparable...

 astronomer al-Khwarizmi (c. 780–850 CE) in 823.

One notable difference between the calendar of that era and the modern form was the date of the epoch
Epoch (reference date)
In the fields of chronology and periodization, an epoch is an instance in time chosen as the origin of a particular era. The "epoch" then serves as a reference point from which time is measured...

 (the fixed reference point at the beginning of year 1), which at that time was one year later than the epoch of the modern calendar.

Most of the present rules of the calendar were in place by 823, according to a treatise by al-Khwarizmi. Al-Khwarizmi's study of the Jewish calendar, "Extraction of the Jewish Era" describes the 19-year intercalation cycle
Metonic cycle
In astronomy and calendar studies, the Metonic cycle or Enneadecaeteris is a period of very close to 19 years which is remarkable for being very nearly a common multiple of the solar year and the synodic month...

, the rules for determining on what day of the week the first day of the month Tishrī
Tishrei
Tishrei or Tishri , Tiberian: ; from Akkadian "Beginning", from "To begin") is the first month of the civil year and the seventh month of the ecclesiastical year in the Hebrew calendar. The name of the month is Babylonian. It is an autumn month of 30 days...

 shall fall, the interval between the Jewish era
Anno Mundi
' , abbreviated as AM or A.M., refers to a Calendar era based on the Biblical creation of the world. Numerous efforts have been made to determine the Biblical date of Creation, yielding varying results. Besides differences in interpretation, which version of the Bible is being referenced also...

 (creation of Adam) and the Seleucid era
Seleucid era
The Seleucid era was a system of numbering years in use by the Seleucid Empire and other countries among the ancient Hellenistic civilizations. The era dates from the return of Seleucus I Nicator to Babylon in 311 BC after his exile in Ptolemaic Egypt, considered by Seleucus and his court to mark...

, and the rules for determining the mean longitude of the sun and the moon using the Jewish calendar.

In 921, Aaron ben Meïr
Aaron ben Meïr
Aaron ben Meïr was a Jewish rabbi, and a Nasi of the Palestinian Gaonate in the first half of the tenth century. His name was brought to light by several fragments discovered in various genizoth Aaron ben Meïr was a Jewish rabbi, and a Nasi (head of the Sanhedrin) of the Palestinian Gaonate in the...

 proposed changes to the calendar. Though the proposals were rejected, they indicate that all of the rules of the modern calendar (except for the epoch) were in place before that date. In 1000, the Muslim chronologist al-Biruni
Al-Biruni
Abū al-Rayḥān Muḥammad ibn Aḥmad al-BīrūnīArabic spelling. . The intermediate form Abū Rayḥān al-Bīrūnī is often used in academic literature...

 described all of the modern rules of the Hebrew calendar, except that he specified three different epochs used by various Jewish communities being one, two, or three years later than the modern epoch.

There is a tradition, first mentioned by Hai Gaon
Hai Gaon
Hai ben Sherira , was a medieval Jewish theologian, rabbi and scholar who served as Gaon of the Talmudic academy of Pumbedita during the early 11th century. He was born in 939 and died on March 28, 1038...

 (d. 1038 CE), that Hillel b. R. Yehuda
Hillel II
Hillel II, also known simply as Hillel held the office of Nasi of the ancient Jewish Sanhedrin between 320 and 385 CE. He was the son and successor of Judah III. He was a Jewish communal and religious authority, circa 330 - 365 CE...

 "in the year 670 of the Seleucid era" (i.e., 358–359 CE) was responsible for the new calculated calendar with a fixed intercalation cycle. Later writers, such as Nachmanides, explained Hai Gaon's words to mean that the entire computed calendar was due to Hillel b. Yehuda in response to persecution of Jews. Maimonides, in the 12th century, stated that the Mishnaic calendar was used "until the days of Abaye and Rava", who flourished c. 320–350 CE, and that the change came when "the land of Israel was destroyed, and no permanent court was left." Taken together, these two traditions suggest that Hillel b. Yehuda (whom they identify with the mid-4th century Jewish patriarch Ioulos, attested in a letter of the Emperor Julian, and the Jewish patriarch Ellel, mentioned by Epiphanius) instituted the computed Hebrew Calendar because of persecution. H. Graetz linked the introduction of the computed calendar to a sharp repression following a failed Jewish insurrection that occurred during the rule of the Christian emperor Constantius
Constantius II
Constantius II , was Roman Emperor from 337 to 361. The second son of Constantine I and Fausta, he ascended to the throne with his brothers Constantine II and Constans upon their father's death....

 and Gallus
Constantius Gallus
Flavius Claudius Constantius Gallus , commonly known as Constantius Gallus, was a member of the Constantinian dynasty and Caesar of the Roman Empire . Gallus was consul three years, from 352 to 354.- Family :...

. A later writer, S. Lieberman, argued instead that the introduction of the fixed calendar was due to measures taken by Christian Roman authorities to prevent the Jewish patriarch from sending calendrical messengers.

Both the tradition that Hillel b. Yehuda instituted the complete computed calendar, and the theory that the computed calendar was introduced due to repression or persecution, have been questioned. Furthermore, two Jewish dates during post-Talmudic times (specifically in 506 and 776) are impossible under the rules of the modern calendar, indicating that its arithmetic rules were developed in Babylonia during the times of the Geonim
Geonim
Geonim were the presidents of the two great Babylonian, Talmudic Academies of Sura and Pumbedita, in the Abbasid Caliphate, and were the generally accepted spiritual leaders of the Jewish community world wide in the early medieval era, in contrast to the Resh Galuta who wielded secular authority...

 (7th to 8th centuries). The Babylonian rules required the delay of the first day of Tishrei when the new moon
New moon
In astronomical terminology, the new moon is the lunar phase that occurs when the Moon, in its monthly orbital motion around Earth, lies between Earth and the Sun, and is therefore in conjunction with the Sun as seen from Earth...

 occurred after noon.

The Talmuds do, however, indicate at least the beginnings of a transition from a purely empirical to a computed calendar. According to a statement attributed to Yose, an Amora who lived during the second half of the 3rd century, the feast of Purim
Purim
Purim is a Jewish holiday that commemorates the deliverance of the Jewish people in the ancient Persian Empire from destruction in the wake of a plot by Haman, a story recorded in the Biblical Book of Esther .Purim is celebrated annually according to the Hebrew calendar on the 14th...

, 14 Adar, could not fall on a Sabbath nor a Monday, lest 10 Tishrei (Yom Kippur
Yom Kippur
Yom Kippur , also known as Day of Atonement, is the holiest and most solemn day of the year for the Jews. Its central themes are atonement and repentance. Jews traditionally observe this holy day with a 25-hour period of fasting and intensive prayer, often spending most of the day in synagogue...

) fall on a Friday or a Sunday. This indicates that, by the time of the redaction of the Jerusalem Talmud (c. 400 CE), there were a fixed number of days in all months from Adar to Elul, also implying that the extra month was already a second Adar added before the regular Adar. In another passage, a sage is reported to have counseled "those who make the computations" not to set the first day of Tishrei or the Day of the Willow on the sabbath. This indicates that there was a group who "made computations" and were in a position to control, to some extent, the day of the week on which Rosh Hashanah would fall.

The Essenes' calendar


Many of the Dead Sea (Qumran) Scrolls have references to a unique calendar, used by the people there, who are often assumed to be Essenes.

The year of this calendar used the ideal Mesopotamian calendar of twelve 30-day months, to which were added 4 days at the equinoxes and solstices (cardinal points), making a total of 364 days.

There was some ambiguity as to whether the cardinal days were at the beginning of the months or at the end, but the clearest calendar attestations give a year of four seasons, each having three months of 30, 30, and 31 days with the cardinal day the extra day at the end, for a total of 91 days, or exactly 13 weeks. Each season started on the 4th day of the week (Wednesday), every year. (Ben-Dov, Head of All Years, p. 16-17)

With only 364 days, it is clear that the calendar would after a few years be very noticeably different from the actual seasons, but there is nothing to indicate what was done about this problem. Various suggestions have been made by scholars. One is that nothing was done and the calendar was allowed to change with respect to the seasons. Another suggestion is that changes were made irregularly, only when the seasonal anomaly was too great to be ignored any longer. (Ben-Dov, Head of All Years, p. 19-20)

The writings often discuss the moon, but the calendar was not based on the movement of the moon any more than indications of the phases of the moon on a modern western calendar indicate that that is a lunar calendar.

Persian civil calendar


Calendrical evidence for the postexilic Persian period is found in papyri
Elephantine papyri
The Elephantine Papyri are a collection of ancient Jewish manuscripts dating from the 5th century BC. They come from a Jewish community at Elephantine, then called Yeb, the island in the Nile at the border of Nubia, which was probably founded as a military installation in about 650 BC during...

 from the Jewish colony at Elephantine
Elephantine
Elephantine is an island in the River Nile, located just downstream of the First Cataract at the southern border of Ancient Egypt. This region is referred to as Upper Egypt because the land is higher than that near the Mediterranean coast. The island may have received its name because it was a...

, in Egypt. These documents show that the Jewish community of Elephantine used the Egyptian
Egyptian calendar
The ancient civil Egyptian calendar had a year that was 360 days long and was divided into 12 months of 30 days each, plus five extra days at the end of the year. The months were divided into three weeks of ten days each...

 and Babylonian
Babylonian calendar
The Babylonian calendar was a lunisolar calendar with years consisting of 12 lunar months, each beginning when a new crescent moon was first sighted low on the western horizon at sunset, plus an intercalary month inserted as needed by decree. The calendar is based on a Sumerian precedecessor...

 calendars.

The Sardica paschal table
Sardica paschal table
The Sardica paschal table or Sardica document is a document from a Latin manuscript of the 7th/8th century AD. It is a copy in Latin translation of the creed of the Eastern Christian bishops attending the Council of Sardica who, fearing that their deliberations would be dominated by Western...

 shows that the Jewish community of some eastern city, possibly Antioch
Antioch
Antioch on the Orontes was an ancient city on the eastern side of the Orontes River. It is near the modern city of Antakya, Turkey.Founded near the end of the 4th century BC by Seleucus I Nicator, one of Alexander the Great's generals, Antioch eventually rivaled Alexandria as the chief city of the...

, used a calendrical scheme that kept Nisan 14 within the limits of the Julian month of March. Some of the dates in the document are clearly corrupt, but they can be emended to make the sixteen years in the table consistent with a regular intercalation scheme. Peter, the bishop of Alexandria (early 4th century CE), mentions that the Jews of his city "hold their Passover according to the course of the moon in the month of Phamenoth
Paremhat
Paremhat , also known as Baramhat, is the seventh month of the Coptic calendar. It lies between March 10 and April 8 of the Gregorian calendar....

, or according to the intercalary month every third year in the month of Pharmuthi
Paremoude
Parmouti , also known as Barmouda, is the eighth month of the Coptic calendar. It lies between April 9 and May 8 of the Gregorian calendar. Paremoude was also the fourth month of the Season of Proyet in Ancient Egypt, when the Nile floods recede and the crops start to grow throughout Egypt...

", suggesting a fairly consistent intercalation scheme that kept Nisan 14 approximately between the Phamenoth 10 (March 6 in the 4th century CE) and Pharmuthi 10 (April 5). Jewish funerary inscriptions from Zoar, south of the Dead Sea, dated from the 3rd to the 5th century CE, indicate that when years were intercalated, the intercalary month was at least sometimes a repeated month of Adar. But the inscriptions reveal no clear pattern of regular intercalations, nor do they indicate any consistent rule for determining the start of the lunar month.

In 1178, Maimonides
Maimonides
Moses ben-Maimon, called Maimonides and also known as Mūsā ibn Maymūn in Arabic, or Rambam , was a preeminent medieval Jewish philosopher and one of the greatest Torah scholars and physicians of the Middle Ages...

 included all the rules for the calculated calendar and their scriptural basis, including the modern epochal year in his work, Mishneh Torah
Mishneh Torah
The Mishneh Torah subtitled Sefer Yad ha-Hazaka is a code of Jewish religious law authored by Maimonides , one of history's foremost rabbis...

. Today, the rules detailed in Maimonides' code are those generally used by Jewish communities throughout the world.

Usage in contemporary Israel


Early Zionist pioneers were impressed by the fact that the calendar preserved by Jews over many centuries in far-flung diasporas, as a matter of religious ritual, was geared to the climate of their original country: the Jewish New Year marks the moment of transition from the dry season to the rainy one, and major Jewish holidays such as Sukkot
Sukkot
Sukkot is a Biblical holiday celebrated on the 15th day of the month of Tishrei . It is one of the three biblically mandated festivals Shalosh regalim on which Hebrews were commanded to make a pilgrimage to the Temple in Jerusalem.The holiday lasts seven days...

, Passover
Passover
Passover is a Jewish holiday and festival. It commemorates the story of the Exodus, in which the ancient Israelites were freed from slavery in Egypt...

, and Shavuot
Shavuot
The festival of is a Jewish holiday that occurs on the sixth day of the Hebrew month of Sivan ....

 correspond to major points of the country's agricultural year such as planting and harvest.

Accordingly, in the early 20th century the Hebrew calendar was re-interpreted as an agricultural rather than religious calendar. The Kibbutz
Kibbutz
A kibbutz is a collective community in Israel that was traditionally based on agriculture. Today, farming has been partly supplanted by other economic branches, including industrial plants and high-tech enterprises. Kibbutzim began as utopian communities, a combination of socialism and Zionism...

 movement was especially inventive in creating new rituals fitting this interpretation.

After the creation of the State of Israel, the Hebrew calendar became one of the official calendars of Israel, along with the Gregorian calendar
Gregorian calendar
The Gregorian calendar, also known as the Western calendar, or Christian calendar, is the internationally accepted civil calendar. It was introduced by Pope Gregory XIII, after whom the calendar was named, by a decree signed on 24 February 1582, a papal bull known by its opening words Inter...

. Holidays and commemorations not derived from previous Jewish tradition were to be fixed according to the Hebrew calendar date. For example, the Israeli Independence Day falls on 5 Iyar
Iyar
Iyar is the eighth month of the civil year and the second month of the ecclesiastical year on the Hebrew calendar. The name is Babylonian in origin. It is a spring month of 29 days. Iyar usually falls in April–June on the Gregorian calendar.In the Hebrew Bible, before the Babylonian Exile, the...

, Jerusalem Reunification Day on 28 Iyar, and the Holocaust Commemoration Day on 27 Nisan
Nisan
Nisan is the first month of the ecclesiastical year and the seventh month of the civil year, on the Hebrew calendar. The name of the month is Babylonian; in the Torah it is called the month of the Aviv, referring to the month in which barley was ripe. It is a spring month of 30 days...

.

Nevertheless, since the 1950s usage of the Hebrew calendar has steadily declined, in favor of the Gregorian calendar. At present, Israelis — except for a minority of the religiously observant — conduct their private and public life according to the Gregorian calendar, although the Hebrew calendar is still widely acknowledged, appearing in public venues such as banks (where it is legal for use on cheques and other documents, though only rarely do people make use of this option) and on the mastheads of newspapers.

The Jewish New Year (Rosh Hashanah) is a two-day public holiday in Israel. However, since the 1980s an increasing number of secular Israelis celebrate the Gregorian New Year (usually known as "Silvester
Silvester
Silvester is used in some countries as a name for New Year's Eve, including Austria, Croatia, the Czech Republic, France, Germany, Hungary, Israel, Italy, Luxembourg, Poland, Slovakia, Switzerland and Slovenia.The origin of the name is Saint Sylvester's Day in the Roman Catholic Church, named...

 Night" — "ליל סילבסטר") on the night between 31 December and 1 January. Prominent Rabbis have on several occasions sharply denounced this practice, but with no noticeable effect on the secularist celebrants. [citation needed]

The disparity between the two calendars is especially noticeable with regard to commemoration of the assassinated Prime Minister Yitzchak Rabin. The official Day of Commemoration, instituted by a special Knesset
Knesset
The Knesset is the unicameral legislature of Israel, located in Givat Ram, Jerusalem.-Role in Israeli Government :The legislative branch of the Israeli government, the Knesset passes all laws, elects the President and Prime Minister , approves the cabinet, and supervises the work of the government...

 law, is marked according to the Hebrew calendar - on 12 Marcheshvan. However, left-leaning Israelis, who revere Rabin as a martyr for the cause of peace and who are predominantly secular, hold their commemoration on 4 November. In some years the two competing Rabin Memorial Days are separated by as much as two weeks.

Wall calendars commonly used in Israel are hybrids. Most are organised according to Gregorian rather than Jewish months, but begin in September, when the Jewish New Year usually falls, and provide the Jewish date in small characters.

Principles


There are three qualities that distinguish one year from another: whether it is a leap year or a common year, on which of four permissible days of the week the year begins, and whether it is a deficient, regular, or complete year. Mathematically, there are 24 (2x4x3) possible combination
Combination
In mathematics a combination is a way of selecting several things out of a larger group, where order does not matter. In smaller cases it is possible to count the number of combinations...

s, but only 14 of them are valid. Each of these patterns is called a keviyah (Hebrew
Hebrew language
Hebrew is a Semitic language of the Afroasiatic language family. Culturally, is it considered by Jews and other religious groups as the language of the Jewish people, though other Jewish languages had originated among diaspora Jews, and the Hebrew language is also used by non-Jewish groups, such...

 קביעה for "a setting" or "an established thing"), and is encoded as a series of three Hebrew letters.

Leap years


The Jewish calendar is based on the Metonic cycle
Metonic cycle
In astronomy and calendar studies, the Metonic cycle or Enneadecaeteris is a period of very close to 19 years which is remarkable for being very nearly a common multiple of the solar year and the synodic month...

 of 19 years, of which 12 are common (non-leap) years of 12 months and 7 are leap years of 13 months. To determine whether a Jewish year is a leap year, one must find its position in the 19-year Metonic cycle
Metonic cycle
In astronomy and calendar studies, the Metonic cycle or Enneadecaeteris is a period of very close to 19 years which is remarkable for being very nearly a common multiple of the solar year and the synodic month...

. This position is calculated by dividing the Jewish year number by 19 and finding the remainder
Remainder
In arithmetic, the remainder is the amount "left over" after the division of two integers which cannot be expressed with an integer quotient....

. For example, Jewish year 5771 divided by 19 results in a remainder of 14, indicating that it is year 14 of the Metonic cycle. Since there is no year 0, a remainder of 0 indicates that the year is year 19 of the cycle. (See also Golden number (time).)

Years 3, 6, 8, 11, 14, 17, and 19 of the Metonic cycle are leap years. To assist in remembering this sequence, some people use the mnemonic Hebrew word GUCHADZaT , where the Hebrew letters gimel-vav-het aleph-dalet-zayin-tet are used as Hebrew numerals
Hebrew numerals
The system of Hebrew numerals is a quasi-decimal alphabetic numeral system using the letters of the Hebrew alphabet.In this system, there is no notation for zero, and the numeric values for individual letters are added together...

 equivalent to 3, 6, 8, 1, 4, 7, 9. The keviyah merely records whether the year is leap or common; פ for p'shutah, meaning simple and indicating a common year, and מ indicating a leap year.

Another memory aid notes that intervals of the major scale
Major scale
In music theory, the major scale or Ionian scale is one of the diatonic scales. It is made up of seven distinct notes, plus an eighth which duplicates the first an octave higher. In solfege these notes correspond to the syllables "Do, Re, Mi, Fa, Sol, La, Ti/Si, ", the "Do" in the parenthesis at...

 follow the same pattern as do Jewish leap years, with do corresponding to year 19 (or 0): a whole step in the scale corresponds to two common years between consecutive leap years, and a half step to one common year between two leap years. This connection with the major scale is more remarkable in the context of 19 equal temperament.

A mathematical way to determine leap year is to calculate the remainder using the following calculation: (7 x the Jewish year number + 1) / 19; if the remainder is less than 7, the year is a leap year. Also, rounding the result of (7 x the Jewish year number + 1) / 13 to the nearest whole number calculates a 0 for leap years and 1 for common years. Therefore the following Excel formulas calculate a "Binary" representation of leap year (the first pair generate a 0 for Leap Year and 1 for Common Year, and the later pair generate TRUE for Leap Year and FALSE for Common Year):

Rosh Hashanah postponement

Day of week Number of days
Monday 353 355 383 385
Tuesday 354 384
Thursday 354 355 383 385
Saturday 353 355 383 385


To calculate the day on which Rosh Hashanah falls, it is necessary to first calculate the molad
Molad
Molad is a Hebrew word meaning "birth" that also generically refers to the time at which the New Moon is "born". The word is ambiguous, however, because depending on the context it could refer to the actual or mean astronomical lunar conjunction , or the molad of the traditional Hebrew...

 (lunar conjunction
Lunar conjunction
A lunar conjunction is the event when the earth, moon and sun, in that order, are approximately in a straight line. It is sometimes referred to as the new moon, though traditionally and Biblically new moon refers to observance by earth bound individuals of the first visible crescent of rebuilding...

 or new moon
New moon
In astronomical terminology, the new moon is the lunar phase that occurs when the Moon, in its monthly orbital motion around Earth, lies between Earth and the Sun, and is therefore in conjunction with the Sun as seen from Earth...

) of Tishrei, and then determine whether the start of the year must be postponed. The molad can be calculated by multiplying the mean length of a lunar month (29 days, 12 hours, and 793 parts) by the elapsed time since another molad whose weekday is known. (There are 1080 "parts" in an hour, making one part equal to 31/3 seconds.) The molad tohu began 2 days, 5 hours, and 204 parts after the beginning of the week.

The rules are complicated by the fact that the months subject to adjustment, Marcheshvan and Kislev, are the eighth and ninth months of the ecclesiastical year while Tishrei is the seventh month. This means that adjustments must be made in one year in anticipation of the day of the week on which Rosh Hashanah will fall in the next year, which may itself be affected by the day on which it will fall in the third year, and so on. The process is further complicated by the need to insert leap months in accordance with their own cycle.

Nevertheless, only four possible adjustments are needed. These are called the Rosh Hashanah postponement rules, or deḥiyyot:
  • If the molad occurs at or later than 18 hours, Rosh Hashanah is postponed a day. This is called deḥiyyah molad zaken, meaning an "old conjunction."
  • If the molad occurs on a Sunday, Wednesday, or Friday, Rosh Hashanah is postponed a day. If deḥiyyah molad zaken places Rosh Hashanah on one of these days, it is postponed a second day. This is called deḥiyyah lo ADU, an acronym meaning "not one, four, or six."


The first of these (deḥiyyah molad zaken) is thought to be a relic of when the calendar was established empirically (although there is some doubt); the second (deḥiyyah lo ADU) is applied for religious reasons.

The last two rules are applied much less frequently and exist to prevent illegal year lengths. Because they apply to the molad, they are never used if another postponement is made. Their names are Hebrew acronyms for the way they are calculated:
  • If the molad in a common year falls on a Tuesday after 9 hours and 204 parts, Rosh Hashanah is postponed to Thursday. This is deḥiyyah GaTaRaD, an acronym meaning "3 (Tuesday), 9, 204."
  • If the molad following a leap year falls on a Monday after 15 hours and 589 parts, Rosh Hashanah is postponed to Tuesday. This is deḥiyyah BeTUTeKaPoT, and acronym for "2 (Monday), 15, 589."


At the innovation of the rabbis, the mathematical calendar has been arranged to ensure that Yom Kippur
Yom Kippur
Yom Kippur , also known as Day of Atonement, is the holiest and most solemn day of the year for the Jews. Its central themes are atonement and repentance. Jews traditionally observe this holy day with a 25-hour period of fasting and intensive prayer, often spending most of the day in synagogue...

 does not fall on a Friday or Sunday, and Hoshana Rabbah does not fall on Shabbat
Shabbat
Shabbat is the seventh day of the Jewish week and a day of rest in Judaism. Shabbat is observed from a few minutes before sunset on Friday evening until a few minutes after when one would expect to be able to see three stars in the sky on Saturday night. The exact times, therefore, differ from...

. These rules have been instituted because Shabbat restrictions also apply to Yom Kippur, so that if Yom Kippur were to fall on Friday, it would not be possible to make necessary preparations for Shabbat (such as candle lighting
Shabbat candles
Shabbat candles are candles lit on Friday nights, 18 minutes before sunset, to usher in the Jewish Sabbath.Lighting Shabbat candles is a rabbinically mandated law. Candlelighting is traditionally done by the woman of the household, but in the absence of a woman, it may be done by man...

). Similarly, if Yom Kippur fell on a Sunday, it would not be possible to make preparations for Yom Kippur because the preceding day is Shabbat. Additionally, the laws of Shabbat override those of Hoshana Rabbah, so that if Hoshana Rabbah were to fall on Shabbat certain rituals that are a part of the Hoshana Rabbah service (such as carrying willows, which is a form of work) could not be performed.

To prevent Yom Kippur (10 Tishrei) from falling on a Friday or Sunday, Rosh Hashanah (1 Tishrei) cannot be a Wednesday or Friday. Likewise, to prevent Hoshana Rabbah (21 Tishrei) from falling on a Saturday, Rosh Hashanah cannot be a Sunday. This leaves only four days on which Rosh Hashanah can fall: Monday, Tuesday, Thursday, and Saturday, which are referred as the "four gates." Each day is associated with a number (its order in the week, starting with Sunday as 1), and these numbers are associated with Hebrew letters. Therefore the keviyah uses the letters ה,ג,ב and ז (representing 2, 3, 5, and 7, for Monday, Tuesday, Thursday, and Saturday) to denote the starting day of the year.

Deficient, regular, and complete years


The postponement of the year is compensated for by adding a day to the second month or removing one from the third month. A Jewish common year can only have 353, 354, or 355 days. A leap year is always 30 days longer, and so can have 383, 384, or 385 days.
  • A chaserah year (Hebrew for "deficient" or "incomplete") is 353 or 383 days long. Both Marcheshvan and Kislev have 29 days. The Hebrew letter ח "het" is used in the keviyah.
  • A kesidrah year ("regular" or "in-order") is 354 or 384 days long. Marcheshvan has 29 days while Kislev has 30 days. The Hebrew letter כ "kaf" is used in the keviyah.
  • A shlemah year ("complete" or "perfect") is 355 or 385 days long. Both Marcheshvan and Kislev have 30 days. The Hebrew letter ש "shin" is used in the keviyah.


Whether a year is deficient, regular, or complete is determined by the time between two adjacent Rosh Hashanah observances and the leap year. While the keviyah is sufficient to describe a year, a variant specifies the day of the week for the first day of Pesach (Passover
Passover
Passover is a Jewish holiday and festival. It commemorates the story of the Exodus, in which the ancient Israelites were freed from slavery in Egypt...

) in lieu of the year length.

A Metonic cycle equates to 235 lunar months in each 19-year cycle. This gives an average of 6939 days, 16 hours, and 595 parts for each cycle. But due to the Rosh Hashanah postponement rules (preceding section) a cycle of 19 Jewish years can be either 6939, 6940, 6941, or 6942 days in duration. Since none of these values is evenly divisible by seven, the Jewish calendar repeats exactly only following 36,288 Metonic cycles, or 689,472 Jewish years. There is a near-repetition every 247 years, except for an excess of 50 minutes (905 parts).

Days of week of holidays


The period from 1 Adar (or Adar II, in leap years) to 29 Heshvan contains all of the festivals specified in the Bible - Purim
Purim
Purim is a Jewish holiday that commemorates the deliverance of the Jewish people in the ancient Persian Empire from destruction in the wake of a plot by Haman, a story recorded in the Biblical Book of Esther .Purim is celebrated annually according to the Hebrew calendar on the 14th...

 (14 Adar), Pesach (15 Nisan), Shavuot
Shavuot
The festival of is a Jewish holiday that occurs on the sixth day of the Hebrew month of Sivan ....

 (6 Sivan), Rosh Hashanah
Rosh Hashanah
Rosh Hashanah , , is the Jewish New Year. It is the first of the High Holy Days or Yamim Nora'im which occur in the autumn...

 (1 Tishrei), Yom Kippur
Yom Kippur
Yom Kippur , also known as Day of Atonement, is the holiest and most solemn day of the year for the Jews. Its central themes are atonement and repentance. Jews traditionally observe this holy day with a 25-hour period of fasting and intensive prayer, often spending most of the day in synagogue...

 (10 Tishrei), Sukkot
Sukkot
Sukkot is a Biblical holiday celebrated on the 15th day of the month of Tishrei . It is one of the three biblically mandated festivals Shalosh regalim on which Hebrews were commanded to make a pilgrimage to the Temple in Jerusalem.The holiday lasts seven days...

 (15 Tishrei), and Shemini Atzeret
Shemini Atzeret
Shemini Atzeret is a Jewish holiday. It is celebrated on the 22nd day of the Hebrew month of Tishrei. In the Diaspora, an additional day is celebrated, the second day being separately referred to as Simchat Torah...

 (22 Tishrei). This period is fixed, during which no adjustments are made.
Purim
Purim
Purim is a Jewish holiday that commemorates the deliverance of the Jewish people in the ancient Persian Empire from destruction in the wake of a plot by Haman, a story recorded in the Biblical Book of Esther .Purim is celebrated annually according to the Hebrew calendar on the 14th...

Passover
Passover
Passover is a Jewish holiday and festival. It commemorates the story of the Exodus, in which the ancient Israelites were freed from slavery in Egypt...


(first day)
Shavuot
Shavuot
The festival of is a Jewish holiday that occurs on the sixth day of the Hebrew month of Sivan ....


(first day)
17 Tammuz/
Tisha B'Av
Tisha B'Av
|Av]],") is an annual fast day in Judaism, named for the ninth day of the month of Av in the Hebrew calendar. The fast commemorates the destruction of both the First Temple and Second Temple in Jerusalem, which occurred about 655 years apart, but on the same Hebrew calendar date...

Rosh Hashanah
Rosh Hashanah
Rosh Hashanah , , is the Jewish New Year. It is the first of the High Holy Days or Yamim Nora'im which occur in the autumn...

/
Sukkot
Sukkot
Sukkot is a Biblical holiday celebrated on the 15th day of the month of Tishrei . It is one of the three biblically mandated festivals Shalosh regalim on which Hebrews were commanded to make a pilgrimage to the Temple in Jerusalem.The holiday lasts seven days...

/
Shmini Atzeret/
(first day)
Yom Kippur
Yom Kippur
Yom Kippur , also known as Day of Atonement, is the holiest and most solemn day of the year for the Jews. Its central themes are atonement and repentance. Jews traditionally observe this holy day with a 25-hour period of fasting and intensive prayer, often spending most of the day in synagogue...

Chanukah
(first day)
10 Tevet
Tenth of Tevet
Tenth of Tevet , the tenth day of the Hebrew month of Tevet, is a minor fast day in Judaism. It is a "low fast" observed from sunrise to sunset. The day has no relationship to Hanukkah, but it happens to follow that festival by a week...

Tu Bishvat
Tu Bishvat
Tu Bishvat or Tu B'Shevat is a minor Jewish holiday, occurring on the 15th day of the Hebrew month of Shevat . It is also called "The New Year of the Trees" or...

Thu Sat Sun Sun* Mon Wed Sun or Mon Sun or Tue Sat or Mon
Fri Sun Mon Sun Tue Thu Mon Tue Mon
Sun Tue Wed Tue Thu Sat Wed or Thu Wed, Thu, or Fri Tue, Wed, or Thu
Tue Thu Fri Thu Sat Mon Fri or Sat Fri or Sun Thu or Sat
*Postponed from Shabbat

Measurement of hours


Every hour is divided into 1080 halakim or parts. A part is 3⅓ seconds or 1/18 minute. The ultimate ancestor of the helek was a small Babylonian time period called a barleycorn, itself equal to 1/72 of a Babylonian time degree (1° of celestial rotation). Actually, the barleycorn or she was the name applied to the smallest units of all Babylonian measurements, whether of length, area, volume, weight, angle, or time.

The weekdays start with Sunday (day 1) and proceed to Saturday (day 7). Since some calculations use division, a remainder of 0 signifies Saturday.

While calculations of days, months and years are based on fixed hours equal to 1/24 of a day, the beginning of each halachic day is based on the local time of sunset
Sunset
Sunset or sundown is the daily disappearance of the Sun below the horizon in the west as a result of Earth's rotation.The time of sunset is defined in astronomy as the moment the trailing edge of the Sun's disk disappears below the horizon in the west...

. The end of the Shabbat and other Jewish holiday
Jewish holiday
Jewish holidays are days observed by Jews as holy or secular commemorations of important events in Jewish history. In Hebrew, Jewish holidays and festivals, depending on their nature, may be called yom tov or chag or ta'anit...

s is based on nightfall (Tzeth haKochabim) which occurs some amount of time, typically 42 to 72 minutes, after sunset. According to Maimonides, nightfall occurs when three medium-sized stars become visible after sunset. By the 17th century this had become three second-magnitude stars. The modern definition is when the center of the sun is 7° below the geometric (airless) horizon, somewhat later than civil twilight at 6°. The beginning of the daytime portion of each day is determined both by dawn and sunrise
Sunrise
Sunrise is the instant at which the upper edge of the Sun appears above the horizon in the east. Sunrise should not be confused with dawn, which is the point at which the sky begins to lighten, some time before the sun itself appears, ending twilight...

. Most halachic times are based on some combination of these four times and vary from day to day throughout the year and also vary significantly depending on location. The daytime hours are often divided into Sha`oth Zemaniyoth or "Halachic hours" by taking the time between sunrise and sunset or between dawn and nightfall and dividing it into 12 equal hours. The nighttime hours are similarly divided into 12 equal portions, albeit a different amount of time than the "hours" of the daytime. The earliest and latest times for Jewish services
Jewish services
Jewish prayer are the prayer recitations that form part of the observance of Judaism. These prayers, often with instructions and commentary, are found in the siddur, the traditional Jewish prayer book....

, the latest time to eat Chametz
Chametz
Chametz, also Chometz, and other spellings transliterated from , are leavened foods that are forbidden on the Jewish holiday of Passover. According to Jewish law, Jews may not own, eat or benefit from chametz during Passover...

 on the day before Passover
Passover
Passover is a Jewish holiday and festival. It commemorates the story of the Exodus, in which the ancient Israelites were freed from slavery in Egypt...

 and many other rules are based on Sha`oth Zemaniyoth. For convenience, the modern day using Sha`oth Zemaniyoth is often discussed as if sunset were at 6:00pm, sunrise at 6:00am and each hour were equal to a fixed hour. For example, halachic noon may be after 1:00pm in some areas during daylight saving time
Daylight saving time
Daylight saving time —also summer time in several countries including in British English and European official terminology —is the practice of temporarily advancing clocks during the summertime so that afternoons have more daylight and mornings have less...

. Within the Mishnah
Mishnah
The Mishnah or Mishna is the first major written redaction of the Jewish oral traditions called the "Oral Torah". It is also the first major work of Rabbinic Judaism. It was redacted c...

, however, the numbering of the hours starts with the "first" hour after the start of the day.

Worked example


Given the length of the year, the length of each month is fixed as described above, so the real problem in determining the calendar for a year is determining the number of days in the year. In the modern calendar this is determined in the following manner.

The day of Rosh Hashanah and the length of the year are determined by the time and the day of the week of the Tishrei molad, that is, the moment of the average conjunction. Given the Tishrei molad of a certain year, the length of the year is determined as follows:

First, one must determined whether each year is an ordinary or leap year by its position in the 19-year Metonic cycle. Years 3, 6, 8, 11, 14, 17, and 19 are leap years.

Secondly, one must determine the number of days between the starting Tishrei molad (TM1) and the Tishrei molad of the next year (TM2). For calendar descriptions in general the day begins at 6 pm, but for the purpose of determining Rosh Hashanah, a molad occurring on or after noon is treated as belonging to the next day (the second deḥiyyah). All months are calculated as 29d, 12h, 44m, 3 1/3s long (MonLen). Therefore, in an ordinary year TM2 occurs 12 x MonLen days after TM1. This is usually 354 calendar days after TM1, but if TM1 is on or after 3:11:20 a.m. and before noon, it will be 355 days. Similarly, in a leap year, TM2 occurs 13 x MonLen days after TM1. This is usually 384 days after TM1, but if TM1 is on or after noon and before 2:27:16 2/3 pm., TM2 will be only 383 days after TM1. In the same way, from TM2 we calculate TM3. Thus the four natural year lengths are 354, 355, 383, and 384 days.

However, because of the holiday rules Rosh Hashanah cannot fall on a Sunday, Wednesday or Friday, so if TM2 is one of those days, Rosh Hashanah in year 2 is postponed by adding one day to year 1 (the first deḥiyyah). To compensate, one day is subtracted from year 2. It is to allow these adjustments that the system allows 385-day years (long leap) and 353-day years(short ordinary) besides the four natural year lengths.

But how can we lengthen year 1 if it is already a long ordinary year of 355 days or shorten year 2 if it is a short leap year of 383 days? That is why we need the third and fourth deḥiyyahs.

If year 1 is already a long ordinary year of 355 days, there will be a problem if TM1 is on a Tuesday, as that means TM2 falls on a Sunday and will have to be postponed, creating a 356-day year. In this case, Rosh Hashanah in year 1 is postponed from Tuesday (the third deḥiyyah). As it cannot be postponed to Wednesday, it is postponed to Thursday, and year 1 ends up with 354 days.

On the other hand, if year 2 is already a short year of 383 days there will be a problem if TM2 is on a Wednesday. because Rosh Hashanah in year 2 will have to be postponed from Wednesday to Thursday and this will cause year 2 to be only 382 days long. In this case, year 2 is extended by one day by postponing Rosh Hashanah in year 3 from Monday to Tuesday (the fourth deḥiyyah ), and year 2 will have 383 days.

Synodic month - the molad interval


A "new moon
New moon
In astronomical terminology, the new moon is the lunar phase that occurs when the Moon, in its monthly orbital motion around Earth, lies between Earth and the Sun, and is therefore in conjunction with the Sun as seen from Earth...

" (astronomically called a lunar conjunction
Lunar conjunction
A lunar conjunction is the event when the earth, moon and sun, in that order, are approximately in a straight line. It is sometimes referred to as the new moon, though traditionally and Biblically new moon refers to observance by earth bound individuals of the first visible crescent of rebuilding...

 and in Hebrew called a molad
Molad
Molad is a Hebrew word meaning "birth" that also generically refers to the time at which the New Moon is "born". The word is ambiguous, however, because depending on the context it could refer to the actual or mean astronomical lunar conjunction , or the molad of the traditional Hebrew...

) is the moment at which the sun and moon are aligned horizontally with respect to a north-south line (technically, they have the same ecliptical longitude). The period between two new moons is a synodic month. The actual length of a synodic month varies from about 29 days 6 hours and 30 minutes (29.27 days) to about 29 days and 20 hours (29.83 days), a variation range of about 13 hours and 30 minutes. Accordingly, for convenience, a long-term average length called the mean synodic month (also called the molad interval) is used. The mean synodic month is days, or 29 days, 12 hours, and 793 parts (44+1/18 minutes) (i.e. 29.530594 days), and is the same value determined by the Babylonians in the System B
Babylonian mathematics
Babylonian mathematics refers to any mathematics of the people of Mesopotamia, from the days of the early Sumerians to the fall of Babylon in 539 BC. Babylonian mathematical texts are plentiful and well edited...

 in about 300 BCE and was adopted by the Greek astronomer Hipparchus
Hipparchus
Hipparchus, the common Latinization of the Greek Hipparkhos, can mean:* Hipparchus, the ancient Greek astronomer** Hipparchic cycle, an astronomical cycle he created** Hipparchus , a lunar crater named in his honour...

 in the 2nd century BC and by the Alexandrian astronomer Ptolemy
Ptolemy
Claudius Ptolemy , was a Roman citizen of Egypt who wrote in Greek. He was a mathematician, astronomer, geographer, astrologer, and poet of a single epigram in the Greek Anthology. He lived in Egypt under Roman rule, and is believed to have been born in the town of Ptolemais Hermiou in the...

 in Almagest
Almagest
The Almagest is a 2nd-century mathematical and astronomical treatise on the apparent motions of the stars and planetary paths. Written in Greek by Claudius Ptolemy, a Roman era scholar of Egypt,...

in the 2nd century CE (who cited Hipparchus as his source). Its remarkable accuracy (less than one second from the true value) is thought to have been achieved using records of lunar eclipses from the 8th to 5th centuries BCE.

This value is as close to the correct value of 29.530589 days as it is possible for a value to come that is rounded off to whole parts (1/18 minute). The discrepancy makes the molad interval about 0.6 seconds too long. Put another way, if the molad is taken as the time of mean conjunction at some reference meridian, then this reference meridian is drifting slowly eastward. If this drift of the reference meridian is traced back to the mid-4th century CE, the traditional date of the introduction of the fixed calendar, then it is found to correspond to a longitude midway between the Nile
Nile
The Nile is a major north-flowing river in North Africa, generally regarded as the longest river in the world. It is long. It runs through the ten countries of Sudan, South Sudan, Burundi, Rwanda, Democratic Republic of the Congo, Tanzania, Kenya, Ethiopia, Uganda and Egypt.The Nile has two major...

 and the end of the Euphrates
Euphrates
The Euphrates is the longest and one of the most historically important rivers of Western Asia. Together with the Tigris, it is one of the two defining rivers of Mesopotamia...

. The modern molad moments match the mean solar times of the lunar conjunction moments near the meridian of Kandahar
Kandahar
Kandahar is the second largest city in Afghanistan, with a population of about 512,200 as of 2011. It is the capital of Kandahar Province, located in the south of the country at about 1,005 m above sea level...

, Afghanistan
Afghanistan
Afghanistan , officially the Islamic Republic of Afghanistan, is a landlocked country located in the centre of Asia, forming South Asia, Central Asia and the Middle East. With a population of about 29 million, it has an area of , making it the 42nd most populous and 41st largest nation in the world...

, more than 30°
Longitude
Longitude is a geographic coordinate that specifies the east-west position of a point on the Earth's surface. It is an angular measurement, usually expressed in degrees, minutes and seconds, and denoted by the Greek letter lambda ....

 east of Jerusalem. Furthermore, due to the eccentricity of Earth's orbit, series of shorter lunations alternate with series of longer lunations. Consequently the actual lunar conjunction moments can range from 12 hours earlier than to 16 hours later than the molad moment, in terms of Jerusalem mean solar time.

Furthermore, the discrepancy between the molad interval and the mean synodic month is accumulating at an accelerating rate, since the mean synodic month is progressively shortening due to gravitational tidal
Tide
Tides are the rise and fall of sea levels caused by the combined effects of the gravitational forces exerted by the moon and the sun and the rotation of the Earth....

 effects. Measured on a strictly uniform time scale, such as that provided by an atomic clock
Atomic clock
An atomic clock is a clock that uses an electronic transition frequency in the microwave, optical, or ultraviolet region of the electromagnetic spectrum of atoms as a frequency standard for its timekeeping element...

, the mean synodic month is becoming gradually longer, but since the tides slow Earth's rotation rate even more, the mean synodic month is becoming gradually shorter in terms of mean solar time.

Seasonal drift


The mean Hebrew calendar year is 365 days 5 hours 55 minutes and 25+25/57 seconds long (365.2468 days) - computed as the molad/monthly interval of 29.530594 days × 235 months in a 19-year metonic cycle ÷ 19 years per cycle. As the present-era mean northward equinoctal year
Tropical year
A tropical year , for general purposes, is the length of time that the Sun takes to return to the same position in the cycle of seasons, as seen from Earth; for example, the time from vernal equinox to vernal equinox, or from summer solstice to summer solstice...

 is 365 days 5 hours 49 minutes 1 second long (365.2424 days), the Hebrew calendar has a "seasonal drift" in relation to the tropical year of about a day every 224 years.

In relation to the Gregorian calendar
Gregorian calendar
The Gregorian calendar, also known as the Western calendar, or Christian calendar, is the internationally accepted civil calendar. It was introduced by Pope Gregory XIII, after whom the calendar was named, by a decree signed on 24 February 1582, a papal bull known by its opening words Inter...

, the mean Gregorian calendar year is 365 days 5 hours 49 minutes and 12 seconds long (365.2425 days), and the drift of the Hebrew calendar in relation to it is about a day every 231 years.

The impact of the drift is reflected in the drift of the date of Passover from the vernal full moon:
Comparison of vernal full moon to
actual dates of Passover: 2001–2020
In Gregorian dates
Year Astronomical vernal full moon Passover*
2001 8 April 8 April
2002 28 March 28 March
2003 16 April 17 April
2004 5 April 6 April
2005 25 March 24 April
2006 13 April 13 April
2007 2 April 3 April
2008 21 March 20 April
2009 9 April 9 April
2010 30 March 30 March
2011 18 April 19 April
2012 6 April 7 April
2013 27 March 26 March
2014 15 April 15 April
2015 4 April 4 April
2016 23 March 23 April
2017 11 April 11 April
2018 31 March 31 March
2019 21 March 20 April
2020 8 April 9 April
*Passover commences at sunset preceding the date indicated.

Implications for Jewish ritual



Although the molad of Tishrei is the only molad moment that is not ritually announced, it is actually the only one that is relevant to the Hebrew calendar, for it determines the provisional date of Rosh Hashanah, subject to the Rosh Hashanah postponement rules. The other monthly molad moments are announced for mystical reasons. With the moladot on average almost 100 minutes late, this means that the molad of Tishrei lands one day later than it ought to in (100 minutes) ÷ (1440 minutes per day) = 5 of 72 years or nearly 7% of years!

Therefore the seemingly small drift of the moladot is already significant enough to affect the date of Rosh Hashanah, which then cascades to many other dates in the calendar year and sometimes, due to the Rosh Hashanah postponement rules, also interacts with the dates of the prior or next year. The molad drift could be corrected by using a progressively shorter molad interval that corresponds to the actual mean lunar conjunction interval at the original molad reference meridian. Furthermore, the molad interval determines the calendar mean year, so using a progressively shorter molad interval would help correct the excessive length of the Hebrew calendar mean year, as well as helping it to "hold onto" the northward equinox for the maximum duration.

When the 19 - year intercalary cycle was finalised in the fourth century AD the earliest Passover (in year 16 of the cycle) coincided with the northward equinox, which means that Passover fell near the first full moon after the northward equinox, or that the northward equinox landed within one lunation before 16 days after the molad of Nisan. This is still the case in about 80% of years, but in about 20% of years Passover is a month late by these criteria (as it was in Hebrew years 5765 and 5768, the 8th and 11th years of the 19-year cycle = Gregorian 2005 and 2008 CE). Presently this occurs after the "premature" insertion of a leap month in years 8, 11, and 19 of each 19-year cycle, which causes the northward equinox to land on exceptionally early Hebrew dates in such years. This problem will get worse over time, and so beginning in Hebrew year 5817 (2057 CE), year 3 of each 19-year cycle will also be a month late. Furthermore, the drift will accelerate in the future as perihelion approaches and then passes the northward equinox, and if the calendar is not amended then Passover will start to land on or after the summer solstice around Hebrew year 16652 (12892 CE). (The exact year when this will begin to occur depends on uncertainties in the future tidal slowing of the Earth rotation rate, and on the accuracy of predictions of precession and Earth axial tilt.)

The seriousness of the spring equinox drift is widely discounted on the grounds that Passover will remain in the spring season for many millennia, and the text of the Torah is generally not interpreted as having specified tight calendrical limits. On the other hand, the mean southward equinoctial year length is considerably shorter, so the Hebrew calendar has been drifting faster with respect to the autumn equinox, and at least part of the harvest festival of Sukkot is already more than a month after the equinox in years 1, 9, and 12 of each 19-year cycle; beginning in Hebrew year 5818 (2057 CE), this will also be the case in year 4. (These are the same year numbers as were mentioned for the spring season in the previous paragraph, except that they get incremented at Rosh Hashanah.) This progressively increases the probability that Sukkot will be cold and wet, making it uncomfortable or impractical to dwell in the traditional succah during Sukkot. The first winter seasonal prayer for rain is not recited until Shemini Atzeret, after the end of Sukkot, yet it is becoming increasingly likely that the rainy season in Israel will start before the end of Sukkot.

No equinox or solstice will ever be more than a day or so away from its mean date according to the solar calendar, while nineteen Jewish years average 6939d 16h 33m 03 1/3s compared to the 6939d 14h 26m 15s of nineteen mean tropical years. This discrepancy has mounted up to six days, which is why the earliest Passover currently falls around 27 March.

"Rectifying" the Hebrew calendar


It has been argued by some that, as the fixed arithmetic Hebrew calendar was established on the authority of Hillel II
Hillel II
Hillel II, also known simply as Hillel held the office of Nasi of the ancient Jewish Sanhedrin between 320 and 385 CE. He was the son and successor of Judah III. He was a Jewish communal and religious authority, circa 330 - 365 CE...

, President of the Sanhedrin
Sanhedrin
The Sanhedrin was an assembly of twenty-three judges appointed in every city in the Biblical Land of Israel.The Great Sanhedrin was the supreme court of ancient Israel made of 71 members...

 in Hebrew year 4119 (358 CE), only an equal authority (the modern Sanhedrin
Sanhedrin
The Sanhedrin was an assembly of twenty-three judges appointed in every city in the Biblical Land of Israel.The Great Sanhedrin was the supreme court of ancient Israel made of 71 members...

) can either amend it or reinstate the observational Hebrew calendar. The attribution of the fixed arithmetic Hebrew calendar solely to Hillel II
Hillel II
Hillel II, also known simply as Hillel held the office of Nasi of the ancient Jewish Sanhedrin between 320 and 385 CE. He was the son and successor of Judah III. He was a Jewish communal and religious authority, circa 330 - 365 CE...

 has, however, been questioned by a few authors, such as Sasha Stern, who claim that the calendar rules developed gradually over several centuries.

Given the importance in Jewish ritual of establishing the accurate timing of monthly and annual times, some futurist writers and researchers have considered whether a "corrected" system of establishing the Hebrew date is required. The Hebrew calendar mean year is more than 6 minutes and 25 seconds in excess of the northern hemisphere spring equinox year, and has "drifted" an average of 7–8 days late relative to the equinox relationship that it originally had. It is not possible, however, for any individual Hebrew date to be a week or more "late", because Hebrew months always begin within a day or two of the molad
Molad
Molad is a Hebrew word meaning "birth" that also generically refers to the time at which the New Moon is "born". The word is ambiguous, however, because depending on the context it could refer to the actual or mean astronomical lunar conjunction , or the molad of the traditional Hebrew...

moment. What happens instead is that the traditional Hebrew calendar "prematurely" inserts a leap month one year before it "should have been" inserted, where "prematurely" means that the insertion causes the spring equinox to land more than 30 days before the latest acceptable moment, thus causing the calendar to run "one month late" until the time when the leap month "should have been" inserted prior to the following spring. This presently happens in 4 years out of every 19-year cycle (years 3, 8, 11, and 19), implying that the Hebrew calendar currently runs "one month late" more than 21% of the time. To a minor degree the tardiness of the calendar is also due to not correcting for the progressively shorter mean astronomical lunation interval — although presently this only accounts for a little over six seconds of the yearly equinox drift, it more importantly accounts for nearly two hours of molad drift relative to actual mean lunar conjunctions, which is enough to cause Rosh HaShanah to start on the "wrong" date in an appreciable number of years.

Dr. Irv Bromberg has proposed a 353-year cycle of 4366 months, which would include 130 leap months, along with use of a progressively shorter molad interval, which would keep an amended fixed arithmetic Hebrew calendar from drifting for more than seven millennia. It takes about 3 centuries for the spring equinox to drift an average of th of a molad interval earlier in the Hebrew calendar. That is a very important time unit, because it can be cancelled by simply truncating a 19-year cycle to 11 years, omitting 8 years including three leap years from the sequence. That is the essential feature of the 353-year leap cycle .

Religious questions abound about how such a system might be implemented and administered throughout the diverse aspects of the world Jewish community.

See also


  • Babylonian calendar
    Babylonian calendar
    The Babylonian calendar was a lunisolar calendar with years consisting of 12 lunar months, each beginning when a new crescent moon was first sighted low on the western horizon at sunset, plus an intercalary month inserted as needed by decree. The calendar is based on a Sumerian precedecessor...

  • Biblical and Talmudic units of measurement
    Biblical and Talmudic units of measurement
    Biblical and Talmudic units of measurement, such as the Omer, used primarily by ancient Israelites, appear frequently within the Hebrew Bible as well as in later Judaic scripture, such as the Mishnah and Talmud...

  • Chronology of the Bible
    Chronology of the Bible
    The chronology of the Bible is the elaborate system of genealogies, generations, reign-periods, and other means by which Hebrew Bible measures the passage of time and thus give a chronological framework to biblical history from the Creation until the historical kingdoms of Israel and Judah.The...

  • Islamic calendar
    Islamic calendar
    The Hijri calendar , also known as the Muslim calendar or Islamic calendar , is a lunar calendar consisting of 12 lunar months in a year of 354 or 355 days. It is used to date events in many Muslim countries , and used by Muslims everywhere to determine the proper day on which to celebrate Islamic...

  • Jewish holidays 2000-2050
    Jewish holidays 2000-2050
    This is an almanac-like listing of major Jewish holidays from 2000 to 2050. All Jewish holidays begin at sundown on the evening before the date shown. On holidays marked "*", Jews are not permitted to work...


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