Julius Caesar, Father of Leap Year

Julius Caesar was behind the origin of leap
year in 45 BC. The early Romans had a 355 day
calendar and to keep festivals occurring around
the same season each year a 22 or 23 day month
was created every second year.

Julius Caesar decided to simplify things and
added days to different months of the year to
create the 365 day calendar, the actual
calculation were made by Caesar's astronomer,
Sosigenes. Every fourth year following the 28th
day of Februarius (February 29th) one day was
to be added, making every fourth year
a leap year.

In 1582, Pope Gregory XIII further refined
the calendar with the rule that leap day would
occur in any year divisible by 4 as described
above.