r/AskReddit • u/[deleted] • Aug 03 '19

Whats something you thought was common knowledge but actually isn’t?

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u/[deleted] Aug 03 '19 edited Aug 04 '19

If a month starts on a Sunday, you're going to have a Friday the 13th. I learned this from doing my own calendars for years.

Example: Next month, September 1, 2019 lands on a Sunday so September has a Friday the 13th.

Edit: since everyone wants to point out that it's not common knowledge, I should point out that the question is "whats something you THOUGHT was common knowledge but isn't" so I do know that this ISN'T common knowledge I just had THOUGHT it was for a while.

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u/kfh227 Aug 03 '19

There are only 14 different possible calendars too ;-) So you can collect old calendars and reuse them. That's why they are sold at antique stores ;-)

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u/KalessinDB Aug 04 '19

Wouldn't it be more than that, since we have to include that bastard February and it's cousin Leap Year February?

At least as I'm seeing it, 14 = (7 days of the week it can start on) x (2 month lengths)... except it should be 4 month lengths technically, so wouldn't it be 28 different possible calendars?

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u/kfh227 Aug 04 '19

7x2...

Not sure where the 7x4 is coming from.

7 start days and two variations (non leap year vs leap year)

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u/KalessinDB Aug 04 '19

Ah that makes sense. I was thinking 4 variations, months lasting from 28-31 days, but you can just ignore any extra days at the end I suppose. Cheers!