Sometimes, I like to use this space for educational purposes. However, this is not the case this week so feel free to continue reading, secure in the knowledge that you will be no smarter when you finish than you were when you began.

As you probably know, 2008 is a leap year. That means that February will have 29 days instead its usual 28. Fortunately for us, that extra day (called “leap day”) will be a Friday and not a Monday.

So, why the extra day? Well, in addition to giving us another Friday (can’t have too many of those), leap years are needed so that our calendar matches up with the Earth's motion around the sun.

We define a year as the period between two successive vernal equinoxes. A vernal equinox is that point at which the sun is directly above the Earth's equator and appears to “turn” from the southern to the northern hemisphere. This is called a tropical year. It takes the name “tropical” from the Greek word “tropos,” which means “to turn,” and not because it wears shirts festooned with pineapples and bongo players. And a tropical year is about 365.2422 days long.

Using our 365-day calendar, we end up with an extra six hours per year. Six hours may not sound like much but over the course of 100 years, we’d be more than 24 days ahead of the seasons. This is not a good situation -- especially if you’re trying to pack for a vacation.

To keep this from happening, the people in charge of such things add an extra day to February every four years (remember, our calendar is off by a quarter-day a year) and everything works out pretty well.

How we came to use the calendar we use today is an interesting story. A long time ago – no matter what calendar you go by – the Romans used a 355-day calendar. This calendar was very complicated and did not match up to the Earth’s movement around the sun. It was so far off, in fact, that some years the Romans would add an entire month to make it sync with the seasons. Since there was no telling when the extra days would be added, planning parties was a real headache.

Julius Caesar, when not inventing salads, was a calendar reformer. In addition to standardizing the beginning date of the year so that it is always Jan. 1, he also did away with adding a month every so many years. Caesar also added 10 days to the Roman calendar to give us (more or less) the 365-day year we still use today. Being emperor, he also got to name a month after himself, which is why every summer we celebrate the 4th of Caesar.

This continued until the 1500s, when Pope Gregory changed the calendar again. His main reason for doing this was so that the date of Easter could be calculated accurately. Because the Julian calendar year was a little too long, the date on which Easter was celebrated would slowly drift forward in relation to the seasons. If left uncorrected, Easter would eventually fall in the same week as Christmas, and no one would know what kind of cards to send to friends and family.