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 (email@example.com) or subscribe to firstname.lastname@example.org (see http://lists.perl.org/ for subscription information) and ask there.
Rich Bowen CPAN ID: RBOW email@example.com http://www.rcbowen.com
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.
perl(1). Date::ICal Reefknot (http://reefknot.org/) Date::Easter Date::Passover Date::Leapyear