ericgrau wrote:Something tells me this still isn't accurate enough. When's the next '00 year that we have to add/subtract a leap year to get it perfect with the earth's orbit around the sun? I leave it as an exercise for the reader.
The commonly proposed rule is to make every year that's an exact multiple of 4000 a non-leap year, making the average length of the year 365.24225 days.
An alternative proposal is to ditch the current practice of skipping leap years at the end of each century and use a more accurate system of skipping a leap-year whenever the year is exactly divisible by 128, making the average calendar year 365.2421875 days.
My personal preference is to ditch the "divisible-by-four" system and just make any year divisible by 5 or 19 a leap-year. This makes the average calendar year 365.2421056263 days long.
The
mean tropical year is measured at 365.24219 days, but is gradually getting smaller because the slowing of the earth's rotation is making the days longer. This means that in the long-run my system would be more accurate than either of those proposals.
(Note, when I say "divisible by 5 or 19" I mean an inclusive or, so that any year divisible by
both 5 and 19 would also be a leap year.)