Leaping into the New Year

There is a February 29th, 2008. 2008 is a leap year. But what's leaping? Well, Christmas, 2007, was on a Tuesday, but Christmas, 2006 was on a Monday. Usually a given calendar date moves up one day each year, because there are 365 days in a (normal) year, just 52 weeks and one day. But (and here's where the idea of "leaping" comes in,) Christmas, 2008 will be on a Thursday. Christmas will "leap over" a Wednesday. The leap year has 366 days, or 52 weeks and two days.

A leap year every four years -- the leap year instituted by Julius Ceasar. This would be fine if the year were exactly 365 1/4 days long. But it isn't. It's a little less, eleven minutes less. Corrections had to be made. In 1562, Pope Gregory instituted the calendar that bears his name, and is the one in use today. He decreed that there were to be leap years every four years, as before, but not on exact centuries. Every (exact) century, like 1700, 1800, 1900, even though it's divisible by 4, is not a leap year. No one was born on February 29, 1900. There was no such date.

But there was an exception: certain centuries would still be leap years, if the year was divisible by 400. Like 1200, 1600, and 2000.

In 2008 we will leap again.

(01/02/08)