One thought on “Odd Day”

  1. One of the characters claims to have had an odd birthday last year and to be having one again next year. How can this be?

    The only eligible people are the ones whose birthdays are on one of those six dates per year that begin with consecutive odd numbers: 1/3, 3/5, 5/7, 7/9, 9/11, and 11/13.

    Each of those only forms an odd day once per century. 1/3 had its day in 2005 and won’t have it again until 2105, and so on for the other five dates.

    So no one can have an odd birthday twice in three years–unless the character doesn’t mean an “odd day birthday” but simply a “birthday made up of only odd numbers.” That is quite common, happening to about 25% of us during every odd-numbered year.

    –Not Just Jealous Because Her Birthday is Loaded with Even Numbers

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