Friday thirteen come on Friday this month

Posted on Saturday, 2011 May 14 by Anton

Somewhere or other I recently mentioned having heard that, because the Gregorian calendar cycle of 400 years is a multiple of 7 days, the 13th of the month is not evenly distributed and falls more often on Friday than on any other day of the week; but I had not done the math myself and did not have the numbers. Now I’ve done it but can’t remember where to post the followup!

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2 Responses to Friday thirteen come on Friday this month

  1. Perry says:
    Sunday, 2011 May 15 at 18:02

    Post it here! 🙂

    Reply
  2. Anton says:
    Sunday, 2011 June 05 at 12:46
      Sunday Monday Tuesday Wednesday Thursday Friday Saturday
    January 13 58 57 57 58 56 58 56
    February 13 56 58 56 58 57 57 58
    March 13 58 56 58 57 57 58 56
    April 13 57 58 56 58 56 58 57
    May 13 58 57 57 58 56 58 56
    June 13 56 58 56 58 57 57 58
    July 13 57 58 56 58 56 58 57
    August 13 56 58 57 57 58 56 58
    September 13 58 56 58 56 58 57 57
    October 13 57 57 58 56 58 56 58
    November 13 58 56 58 57 57 58 56
    December 13 58 56 58 56 58 57 57
    687 685 685 687 684 688 684
    Reply

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