Why do we have leap years?

With 2012 being a leap year, it is a good time to remind ourselves why it is that we add an extra day to our calendar almost every four years.

The answer, simply put, is that the Earth doesn't take exactly 365 days to orbit the sun. It's actually closer to 365.242 days. While that may not seem like much, it amounts to almost six extra hours a year, which does add up over the long run.

A leap year helps to prevent the shift that would happen in our calendars because of these extra hours. Without it, our calendar would eventually fall out of sync with the weather. In 100 years, our calendar would be about 24 days off, and before we knew it, we'd be seeing winter-like conditions in July and have warm, sunny Decembers.

via ca.news.yahoo.com