It's Leap Day,

a.k.a. the Brigadoon of the Gregorian calendar, when the swirling flurries of midwinter part every four years to give us one more day of the second month of the year. This one's a particularly nice one, too, so if you're out there enjoying it take care not to tarry too long, lest you be trapped in cold and dark February until 2008! I think we need more such days in our calendar - a May 32st that appears every seven years, a July 4th that repeats itself until you've had your fill of sun, surf, and hot dogs, and an October 0th in any year that ends with a prime number - just to keep things interesting. The Mesoamericans found a clever way to build such reccurring fun into their timekeeping by interlocking two counts, the 360(+5)-day solar year and the 260-day ritual calendar, so that the same combination of solar day and ritual day only occurs once every fifty-two years. The Precolumbian Mexican calendar also happens to be far more accurate than our own system, and in fact is second only to modern astronomical observation in its precision. Of course the Mesoamericans also practiced large-scale human sacrifice on a regular basis, but we all have our quirks...