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From: @S1-A.ARPA,@MIT-MC.ARPA:Lynn.ES@Xerox.ARPA
Newsgroups: net.space
Subject: Re: Precession of the equinoxes
Message-ID: <2993@mordor.UUCP>
Date: Thu, 8-Aug-85 12:36:18 EDT
Article-I.D.: mordor.2993
Posted: Thu Aug  8 12:36:18 1985
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From: Lynn.ES@Xerox.ARPA

Contrary to previous statements made here, the precession of the
equinoxes IS related to the Gregorian Calendar.  Without precession, the
seasons would reoccur every 365.2564 days (a sidereal year), and thus
occasional EXTRA leap years would be needed to cause the average year to
be more than 365.25 days.  With precession, the seasons reoccur every
365.2422 days, and thus occasional dropped leap years are needed (3 out
of every 4 century years are dropped).  

In other words, the earth reaches the point where its pole points most
nearly toward the sun (beginning of summer) slightly earlier due to
precession (movement of the direction of that pole).  Another way of
viewing it is that our seasons cycle 25,799 times while we make 25,800
trips around the sun, the difference of one being that our axis rotated
once in that time period due to precession.

/Don Lynn