In ancient times, when calendars were first put into place, the
year-measured by the cycle of changing seasons-was divided into months.
The lengths of the months varied slightly from one culture to the next,
but the basic length-from 28 to 31 days-was consistent across many
cultures. That number of days was based on the cycle of the moon, which
lasts about 29 and one-half days and is easily noticed by just observing
the moonlit sky. The months could not all have the same number of days
because the number of days in a year, approximately 365, is not
divisible by 28, 29, 30, or 31.
In the time of Roman emperor Julius Caesar, who instituted the Julian
calendar in 45 b.c., it was decided that all months would have 30 or 31
days, except February, which at that time had 29 days. Why did February
get short-changed? Before the Julian calendar, the new year began in
March, and perhaps simply because February was the last month of the
year, it was seen as the logical choice for having the fewest number of
days.
One version of calendar history relates how February came to have 28
days. After Julius Caesar's death, the month that was then known as
Quintilis was renamed July in his honor. During the reign of Julius's
successor, Augustus Caesar, the month that then had the name Sextilis
was renamed in honor of the new emperor as August. While July had 31
days, August only had 30, and in order to make his month as long (and as
important) as Julius's month, Augustus took a day from February and
added it to August. From then on August had 31 days and February 28
(except on leap years, when it once again has 29 days).