Year 399 BC was a year of the pre-Julian Roman calendar

Roman calendar

The Roman calendar changed its form several times in the time between the founding of Rome and the fall of the Roman Empire. This article generally discusses the early Roman or pre-Julian calendars...

. At the time, it was known as the Year of the Tribunate of Augurinus, Longus, Priscus, Cicurinus, Rufus and Philo (or, less frequently, year 355 Ab urbe condita

Ab urbe condita

Ab urbe condita is Latin for "from the founding of the City ", traditionally set in 753 BC. AUC is a year-numbering system used by some ancient Roman historians to identify particular Roman years...

). The denomination 399 BC for this year has been used since the early medieval period, when the Anno Domini

Anno Domini

and Before Christ are designations used to label or number years used with the Julian and Gregorian calendars....

 calendar era

Calendar era

A calendar era is the year numbering system used by a calendar. For example, the Gregorian calendar numbers its years in the Western Christian era . The instant, date, or year from which time is marked is called the epoch of the era...

 became the prevalent method in Europe for naming years.

• February 15 – The Greek
  Ancient Greece
  Ancient Greece is a civilization belonging to a period of Greek history that lasted from the Archaic period of the 8th to 6th centuries BC to the end of antiquity. Immediately following this period was the beginning of the Early Middle Ages and the Byzantine era. Included in Ancient Greece is the...
  
   philosopher Socrates
  Socrates
  Socrates was a classical Greek Athenian philosopher. Credited as one of the founders of Western philosophy, he is an enigmatic figure known chiefly through the accounts of later classical writers, especially the writings of his students Plato and Xenophon, and the plays of his contemporary ...
  
   is sentenced to death by Athenian
  Athens
  Athens , is the capital and largest city of Greece. Athens dominates the Attica region and is one of the world's oldest cities, as its recorded history spans around 3,400 years. Classical Athens was a powerful city-state...
  
   authorities, condemned for impiety
  Impiety
  Impiety is classically a lack of proper concern for the obligations owed to public religious observation or cult. Impiety was a main Pagan objection to Christianity, for unlike other initiates into mystery religions, early Christians refused to cast a pinch of incense before the images of the gods,...
  
   and the corruption
  Corruption
  Corruption usually refers to spiritual or moral impurity.Corruption may also refer to:* Corruption , an American crime film* Corruption , a British horror film...
  
   of youth.