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    SubjectRe: February 30th 2000
    Date
    From
    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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