Leap Year Leap Year

We add an extra day to February this year so we remain in sync with the astronomical seasons. We need to add a day about every four years. The solar year, the time it take the sun to appear directly over the equator (Vernal Equinox) and then re-appear takes a bit over one year. In fact that takes 365.24 days. After four years we accrue an extra day. No big deal you say but if we didn’t adjust our calendars in forty years, for example the beginning of spring would be almost in early April instead of the March 20-21 range. Similarly, all of the astronomical dates marking the seasons would be pushed farther and farther back. We use the Gregorian calendar. This calendar has been around since 1582 but we adopted it in September 1752. I’ll confuse you now. Every leap year is divisible by four but if that year is divisible by 100 then it is not a leap year unless of course that year is divisible by 400. So the year 2000 was a leap year but only after the third check was considered. Mathematically the longest time between two leap years is eight years. That won’t happen until 2096 and 2104. If we didn’t care about the seasons beginning roughly the same time every year then we wouldn’t have to add a day every four years except that after one hundred years our calendar would be nearly a month ahead. It would be weird having the calendar read January 21st when in terms of seasons it would only be December 28th. I was hoping that extra day this month would add another snowy day to a snowy winter...oh well.  ¶ 9:52 PM