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Date::SundayLetter - Calculates the Sunday Letters for a given year


  use Date::SundayLetter;
  $letter = sundayletter( 1996 );

  - or just - 

  $letter = letter( 1996 );


Sunday Letters are an important concept from calendrics. Stated very simply, the sunday letter represents how many days after January 1 the first Sunday of the year is. Knowing the makes it easy to calculate the day of the week of a given day, when Easter falls, and a variety of other things.

There is a full treatment of Sunday Latters in The Oxford Companion to the Year (Blackburn, Holford-Strevens).

For example, the following table shows the Sunday Letters, given the day of the week of January 1:

 1 January      First Sunday    Sunday Letter
 Sunday         1 January       A
 Monday         7 January       G
 Tuesday        6 January       F
 Wednesday      5 January       E
 Thursday       4 January       D
 Friday         3 January       C
 Saturday       2 January       B

In leap years, you have two Sunday Letters. After leap day, you have a Sunday Letter calculated with the usual formulae. Before leap day, the Sunday Letter is one place ahead of that (with A being considered one latter after G).

Given the Sunday Letter and the Golden Number (see Date::GoldenNumber), you can immediately look up the dates for Easter (Gregorian or Julian) in a simple table. That is, if you happen to have said table. I'll try to put this table on my web site, but I need to ask the authors of The Oxford Companion first.


For support, email me directly ( or subscribe to (see for subscription information) and ask there.


        Rich Bowen
        CPAN ID: RBOW


Copyright (c) 2001 Rich Bowen. All rights reserved. This program is free software; you can redistribute it and/or modify it under the same terms as Perl itself.

The full text of the license can be found in the LICENSE file included with this module.


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