• Limonene@lemmy.world
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    3 months ago

    Unfortunately this won’t happen until October 31st 2600. Starting on March 1st in the year 2600, the Julian calendar (popular in centuries past, and still used in a few places) will differ by 18 days from the Gregorian calendar (the current worldwide standard calendar).

    It happens that October 31st in the year 2600 lands on a Friday, and so the Julian October 13th, which lands on that same day, is also a Friday.

    There may be a sooner Friday the 13th that lands on Halloween, if you know of other obscure calendars like the Hebrew, Islamic, or Chinese calendars. I don’t know enough about those to check.

    • Ultraviolet@lemmy.world
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      3 months ago

      It’s also always either 6 or 11 years (or 7 in very rare cases, when you’re on both sides of a skipped leap year like 1900 or 2100) between “day X falls on day of the week Y” events unless you’re talking about February 29.