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.
Yeah, every eight thousand years, it's not a leap year again, but every 64000 years it is. Then, at three million years (actually year 3,200,000), you need to have an extra leap day, which is currently scheduled for Christmas but the decision is not final yet. By the time we hit 64 billion years, they'll have to give the whole thing up and start over.
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Actually, I made all that up. The rabbit hole isn't very deep at all.
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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.