Proleptic calendars

John Cowan cowan at
Wed Oct 7 16:45:48 UTC 1998

Here's another specific reference, from

# Every date recorded in history prior to October 15, 1582 (Gregorian), # such as the coronation of Charlemagne as Holy Roman Emperor on
# Christmas day in the year 800, is a date in the Julian Calendar, since
# on those dates the Gregorian Calendar had not yet been invented.

# We can, however, identify particular days prior to October 15, 1582
# (Gregorian), by means of dates in the Gregorian Calendar simply by
# projecting the Gregorian dating system back beyond the time of its
# implementation.  A calendar obtained by extension earlier in time
# than its invention or implementation is called the "proleptic"
# version of the calendar, and thus we obtain the Proleptic Gregorian
# Calendar. The Julian Calendar also can be extended backward as the
# Proleptic Julian Calendar.

# For example, even though the Gregorian Calendar was implemented on
# October 15, 1582 (Gregorian) we can still say that the date of the
# day one year before was October 15, 1581 (Gregorian), even though
# people alive on that day would have said that the date was October 5,
# 1581 (the Julian date at that time). As another example, the date
# of the coronation of Charlemagne, December 25, 800, in the Julian
# Calendar, was December 29, 800, in the Proleptic Gregorian Calendar.

John Cowan		cowan at
	You tollerday donsk?  N.  You tolkatiff scowegian?  Nn.
	You spigotty anglease?  Nnn.  You phonio saxo?  Nnnn.
		Clear all so!  'Tis a Jute.... (Finnegans Wake 16.5)

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