Today it was February 29th; a leap day in a leap year. And for a lot of people the only time in 4 years they can celebrate their birthday. A leap year is a year in which an extra day in added to the calendar in order to synchronize it with the seasons. Since the tropical year is 365.242190 days long, a leap year must be added roughly once every four years (four times the fractional day gives ). In a leap year, the extra day (known as a leap day) is added at the end of February, giving it 29 instead of the usual 28 days.
In the Gregorian calendar currently in use worldwide (except perhaps the Russian and Iranian calendars), there is a leap year every year divisible by four except for years which are both divisible by 100 and not divisible by 400. Therefore, the year 2000 was a leap year, but the years 1700, 1800, and 1900 were not. The complete list of leap years in the first half of the 21st century is therefore 2000, 2004, 2008, 2012, 2016, 2020, 2024, 2028, 2032, 2036, 2040, 2044, and 2048.
The extra rule involving centuries is an additional correction to make up for the fact that one extra day every four years is slightly too much correction (). This scheme results in the vernal equinox gradually shifting its date between March 19 and 21, being shifted once every leap year, and then being abruptly shifted in non-leap centuries.
Confusing? Well I know I was when I read this.
Anyway: I will not have a chance to write my Blog on Februari 29th until 4 years from now: 2008. Wow. I’l be 41 then.
Some trivia: In any ten year period, what’s the minimum number of leap years? What’s the maximum?
Answer:
Minimum: 1 (2097-2107 would only have one leap year, 2104! 2100 is not a leap year (as explained before).
Maximum: 3 (1996-2006 would have 1996, 2000, 2004)
Also: 2004 is a leap year, with 29 days in February. February has five Sundays – it starts and ends on a Sunday. Between 1904 and 2096, leap years repeat every 28 years which means that the last time February had 5 Sundays was in 1976 and next time will be in 2032.
Have a nice leap year!