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Path: utzoo!linus!philabs!seismo!harpo!ihnp4!zehntel!tektronix!orca!rogerc
From: rogerc@orca.UUCP (Roger M. Christal)
Newsgroups: net.general
Subject: Re: Date Algorithm
Message-ID: <486@orca.UUCP>
Date: Thu, 19-Jan-84 14:45:53 EST
Article-I.D.: orca.486
Posted: Thu Jan 19 14:45:53 1984
Date-Received: Sat, 28-Jan-84 02:35:02 EST
Organization: Tektronix, Wilsonville OR.
Lines: 43


Here is the algorithm for computing the day of the week for any
given date (in this century at least).

First, each month is given a number value.

January = 1      July = 0
February = 4     August = 3
March = 4        September = 6
April = 0        October = 1
May = 2          November = 4
June = 5         December = 6

When doing the calculation for a leap year, remember to subtract 1
from January or Febuary dates.

Add:  the year         (modulo 1900 or whatever; 1953 means 53)
      the INT(year/4)  (again; 1953 means 53; INT(53/4) = 12)
      day of month
      month code       (as above)

Divide the above answer by 7 and use the remainder as the day of the 
week; Saturday = 0.

Day Of Week = MOD7 ((year) + INT (year / 4) + (day of month) + (month code))

Example:

I was born on Easter Sunday, 1947.  The date is April 6.

year + INT(year/4) + day + month code

 47  +     11      +  6  +    0       =   64

MOD7 (64) = 1, or Sunday!


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