J. Scott Kasten wrote:
> Sorry, but no, we're not. The exact time measurement for a year
> is 365.24219878... days. We round that off to 365.25 for conveininece
> to get a leap day every four years. However, the decimal is less
> than .25, so after 100 years, we end up ahead. Thus centuries
> are not supposed to be leap years normally, in order to "down correct"
> for the .25 estimate. Now, the part .00219878... remaining, works
> out to be an extra day every 400 years.
Not quite.
Our current (gregorian) rules come to
365 + 1/4 - 1/100 + 1/400 = 365.2425
The difference with 365.24219878 is: .00030122, which means that every
3320 years or so, we're having one too many leap years. So, I would
suggest that we make the year 3300 a leap year. And 6600, 9900, 13300
and so on.... (*)
However, the global temperature of the earth influences the turning of
the earth enough that we can't predict the exact number of turns
around its axis that long head.... So, it doesn't make sense to try
and fix a rule right now that will be wrong by the time it first comes
into action...
By the way, my encyclopedia says there are 365.2428933 days in a year,
which would require us to have to one -=less=- leapyear every 2500
years.
Some quick websearching gives:
http://www.50megs.com/aalembert/y2kco.html
that mentions: 365.2422454...
For a quick laugh check out:
http://www.europa.com/edge/pyramid.html
which mentions that the exact length of the year is 365.24 days. (And
implies that the egyptians who built the pyramids used tenths of an
inch as a measure of length.)
http://www.johnpratt.com/items/calendar/cal_intro.html mentions
365.242 as the "TRUE" value.
http://www.mathematik.uni-bielefeld.de/~sillke/ALGORITHMS/calendar/ancient-time-formular
mentions: 365,24219878 and 365,2422 , which are actually pretty close to
each other. The extra leap year shifts only by 13 years or so, which
wouldn't make a difference for a good 20000 years......
Roger.
(*) The century closest to n*3320, that isn't already a leap year....
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