Just wanted to get the date for at least one post to read February 29th, 2004:

"A leap year is a year in which an extra day in added to the calendar in order to synchronize it with the seasons. Since the tropical year is 365.242190 days long, a leap year must be added roughly once every four years (four times the fractional day gives ). In a leap year, the extra day (known as a leap day) is added at the end of February, giving it 29 instead of the usual 28 days.

The leap year was introduced in the Julian calendar in 46 BC. However, around 10 BC, it was found that the priests in charge of computing the calendar had been adding leap years every three years instead of the four decreed by Caesar (Vardi 1991, p. 239). As a result of this error, no more leap years were added until 8 AD. Leap years were therefore 45 BC, 42 BC, 39 BC, 36 BC, 33 BC, 30 BC, 27 BC, 24 BC, 21 BC, 18 BC, 15 BC, 12 BC, 9 BC, 8 AD, 12 AD, and every fourth year thereafter (Tøndering), until the Gregorian calendar was introduced (resulting in skipping three out of every four centuries). The UNIX command cal incorrectly lists 4 AD as a leap year (Vardi 1991)."