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    Re: What time is it, really?
    From: Gary LaPook
    Date: 2008 Jul 18, 13:35 -0700

    The Gregorian calendar was promulgated by Pope Gregory in 1582 to
    correct the deficiency in the then current Julian calendar which had
    caused the equinox to slip by 11 days. (England did not adopt the new
    calendar until 1752.) The Julian calendar applied a leap day every
    four years making the average solar year 365.25 days and this had
    caused too much of a correction since the average year is not quite
    that long which caused the 11 day slip over the centuries. Gregory's
    calendar eliminated 3 leap days every four hundred years, (100 leap
    days under the Julian calendar and only 97 leap days under the
    Gregorian calendar in every 400 year period.) This was accomplished by
    eliminating leap days in century years unless the century was
    divisible by 400 (2000 was a leap year while 1700, 1800 and 1900 were
    not) while the Julian calendar makes every century year a leap year
    since century years are all divisible by 4. This fraction, 97/100
    (making a year 365.24 days), closely approximates the actual length of
    a solar year which is actually 365.24219878 days, so the current
    calendar accumulates one day of error with respect to the solar year
    about every 3300 years.
    On Jul 18, 10:32 am, Bill  wrote:
    > Greg R. Wrote
    > > K, that's one "extra" day than the annual allotment of 365, so I go
    > > back to my original question about why we don't need leap-days every
    > > year instead of every 4 years or so (something sticks in my mind about
    > > it being 365 1/4 rotations/year(?) - which would jibe with 1 leap-day
    > > every 4 years or so).
    > Correct.  It takes almost 365.25 days for the earth to make one complete
    > revolution around the sun.  The extra 0.25 day would be a bit much to handle
    > time wise, so we stop at 365.  Which leaves us a bit more shy of completing
    > a full revolution each year after leap year.  The extra day in a leap year
    > every 4 years gets us back on track (mostly).  Since the time to orbit the
    > sun is not precisely 365.25 days, we have have the exceptions where there is
    > no leap year to even things out.
    > Bill B.
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