Feb 27 2011

Why do we have leap years?

Category: Science


A leap year is basically a system that allows for the calendar year to stay in sync with the astronomical year. An astronomical year, or the time it takes for the earth to rotate the sun, is 365 days, 5 hrs, 48 min, and 46 seconds. The extra day in a leap year tries to correct this disparity by adding an extra day every 4 years.

So the rule for leap years is:

  • Every year that is divisible by 4 is a leap year (February 29th is observed),
  • EXCEPT the last year of each century, such as 1900, which is NOT a leap year,
  • EXCEPT when the number of the century is a multiple of 4, such as 2000, which IS a leap year,
  • EXCEPT the year 4000 and its later multiples (8000, 12000, etc) which are NOT leap years.


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