Why wasn't 1900 a leap year?

picqero

Leap years occur every 4 years, except those years which are divisible by 100 but not by 400, thus 1900 wasn't a leap year. Mar 13 05, 5:14 AM

elizabethmc

Why is that though? Mar 13 05, 5:22 AM

Flynn_17

Why the leap year or why the weird rule? Mar 13 05, 5:42 AM

elizabethmc

the silly rule Mar 13 05, 6:13 AM

SOTHC

http://www.timeanddate.com/date/leapyear.html should explain your query Mar 13 05, 6:19 AM

gtho4

It's to keep the year in alignment with reality, e.g. Consider a little astronomy and arithmetic. It turns out that our year, the time it takes for the earth to make a single revolution around the sun, is very close to 365.2422 days. If we simply make every fourth year a leap year, we have 365.25 day years, not far off and that .0078 day difference is only about 11 minutes and 14 seconds. (You can easily check that by multiplying .0078 day x 24 hours/day x 60 minutes/hour.) However that small annual accumulation of .0078 day will lead to a full day in about 128 years. (Calculating that is still easier. Enter .0078 in your calculator and press the 1/x key, immediately converting days/year to years/day.) To further correct for this, our current Gregorian calendar makes two adjustments: (1) even though they are clearly divisible by four, years divisible by 100 are not leap years, (2) except for those divisible by 400 which are leap years. Thus 1900 was not a leap year, but this year we have the most unusual case of all -- 2000 is divisible by 400 so it is a leap year. This remarkable situation will not occur again until the year 2400. http://www.acsu.buffalo.edu/~insrisg/nature/nw00/calendar.html Mar 13 05, 6:27 AM

elizabethmc

Thank-you, I understand now... Mar 13 05, 6:39 AM

picqero

My original posting was a bit unclear. Years divisible by 100 are not leap years unless they are also divisible by 400. Hence 1700, 1800, and 1900 weren't leap years. gtho's posting explains the reason very well. Mar 13 05, 7:24 AM

Halcyon91

When is the next leap year? Mar 15 05, 2:21 PM

elizabethmc

2008 Mar 15 05, 2:47 PM