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How many days in a year?

January 1, 2007 pm31 8:59 pm

Ok, so two posts in one.

Puzzle

Today is New Years Day. This year, New Years Day falls on a Monday. Is that the most likely day for New Years, the least likely, or somewhere in between?

Before you jump up and down and say “of course Monday is just as likely as any other day” collect some empirical data, and see what it shows.

Conundrum

Not from me. I have linked Phil Plait’s Bad Astronomy site. Phil has a devilishly easy time making the question “What is a Year?” far more intricate than I would have imagined.

2 Comments leave one →
  1. mark permalink
    January 9, 2007 pm31 10:47 pm 10:47 pm

    I was a little surprised at the result I got when looking at empirical results. I used an Oracle database at work, which uses the Julian calendar for dates before 1583 and the Gregorian calendar for dates thereafter.

    With the Julian calendar, the day of the week for New Years Day repeats on a 28-year cycle with each day of the week occurring 4 times. So Monday is just as likely as any other day.

    With the Gregorian calendar, the day of the week for New Years Day repeats on a 400-year cycle. Friday, Sunday and Tuesday each occur 58 times during any 400 year stretch. Wednesday and Thursday each occur 57 times. And Monday and Saturday each occur 56 times. So New Years Day is least likely to fall on Monday (or Saturday) with the Gregorian calendar.

  2. April 14, 2008 am30 12:44 am 12:44 am

    WEIRD

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