Is every 4th year a leap year, except century years that end in "00"

Every year whose number is divisible by 4 is a leap year, unless it ends in 00 and is not divisible by 400; then it is not a leap year. However, if the year ends in 00 and is also divisible by 400 then it IS a leap year. Thus, 1800 and 1900 were not leap years, but 2000 WAS a leap year; 2100, 2200, and 2300 will not be leap years, but 2400 will be one; 2500, 2600, and 2700 will not be leap years, but 2800 will be one, etc.
Even this system will gradually accumulate an extra day and there are suggestions that the year 4000 not be a leap year. However that is a long way from now and no official decision has been made for this.

As far as I know...the exact length of an year is 365days, 5 hours 46 minutes...and some seconds. Which means that you've to add an extra day after every 4 years if you round up the 5hr46min to 6 hours. That means that after a 100years, you end up with an extra 1400minutes (approx), which come up to 24hrs. Because of this another extra day is added after a century, which is not part of the main leap year. This is just what I heard and calculated. I think you can have a leap year on 00s as well, I maybe wrong though.

No. 1896 and 1900 were leap years. It's century years that are evenly divisible by 400 that are not leap years. This is the main difference between the Julian and the Gregorian calendars. Britain and the United States didn't switch to the Gregorian calendar until 1752. They lost 11 days when they did that. Russia didn't switch until 1920. The rest of Europe made the switch in 1588. George Washington was grumpy and didn't want to make the switch. Jefferson was all for it. Jefferson and Franklin were scientifically enlightened and understood WHY the switch was necessary. It made keeping shipping schedules a mental nightmare. You think keeping 43 time zones straight in your head is mentally challenging? Try 11 days.


http://www.cslib.org/CalendarChange.htm