Proleptic Gregorian (was Re: Functions add/diff/cmp for xtime)

Paul Eggert eggert at
Wed Oct 7 18:50:25 UTC 1998

   Date: Wed, 7 Oct 1998 07:55:02 -0700 (PDT)
   From: Rich Wales <richw at>

   So, the "proleptic Gregorian" calendar would be the result of extending
   the Gregorian calendar back into the past, before it came into use in a
   given location, or even before it was invented.

Actually, you've got it backwards.  Strictly speaking, the proleptic
Gregorian calendar refers to the future, not to the past.  That is, we
assume that the Gregorian calendar will be used indefinitely into the
future.  The term ``proleptic'' is a misnomer when applied to
backwards extrapolation of a calendar, since the term ``proleptic''
refers to the future, not the past.

However, this misnomer is in common use among the calendrical cognoscenti.

This point is covered in footnote 4 on page 35 of the following reference:

Nachum Dershowitz and Edward M Reingold
Calendrical Calculations
Cambridge University Press (1997)

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