And for a really nice little history on the calendar, visit The Writer's Almanac. Here's a start:
Today is Leap Day, the extra day that we tack on to February every four years to keep the calendar in time with the seasons. We do this because the Earth does not orbit the sun in a nice round 365 days, but rather in 365 days, 5 hours, 48 minutes, and 45 seconds.
The Egyptians were one of the first civilizations to develop a calendar with 12 months and 365 days. When Julius Caesar rose to power, the Romans were using a calendar that was so faulty they often had to add an extra 80 days to the year. In 46 B.C., after his affair with Cleopatra, Caesar chose to adopt the superior Egyptian calendar, and this became known as the Julian calendar. In the first version of the Julian calendar, February had 29 days most years and 30 days in leap years. Caesar named the month of July after himself, so when Augustus came to power, he decided he needed a month too. He named August after himself, but he had to steal a day from February in order to make August as long as July.