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Re: historical astronomy question



Regarding:

November 24, 1639 on the Julian calendar corresponds to
December 7, 1639 on the Gregorian calendar. I confirm the
December 4 date of the transit by Starry Night Pro.

Leigh

So how do you resolve the 3-day discrepancy?

Larry

It seems to me that November 24, 1639 on the Julian calendar corresponds
to December 4, 1639 on the Gregorian calendar *not* to December 7, 1639.
Currently for the 20th and 21st centuries there is a 13 day shift
between these two calendars. But in the 17th century there was only a
*10 day* shift between these 2 calendars. Since that time the years
1700, 1800, & 1900 were not leap years for the Gregorian calendars but
were leap years for the Julian calendar, thus causing a further shift by
another 3 days. (Technically, I suppose that the part of the 17th
century that ranged from Mar. 01, 1700 to Dec. 31, 1700, Gregorian had
an 11 day rather than a 10 day shift w.r.t. the Julian calendar.)

David Bowman
David_Bowman@georgetowncollege.edu