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Fri Sep 13, 2019, 02:32 AM

On Average, the Harvest Moon Occurs on Friday the 13th Every 210 Years.

For areas west of the Eastern Time zone, today is a very rare occurrence (once every 210 years on average) of the Harvest Moon beaming on Friday the Thirteenth.

The frequency of the harvest moon falling on "Friday The Thirteen" is easy to calculate. You can start by observing that the chance of the full moon falling on the thirteen of any month is about one in 30, or once every 2.5 years. Narrowing the day of the week to Friday means multiplying 2.5 by 7 which yields 17.5 years. Narrowing the month to September means multiplying 17.5 years by 12 which yields 210 years.



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Reply On Average, the Harvest Moon Occurs on Friday the 13th Every 210 Years. (Original post)
John1956PA Sep 13 OP
CaliforniaPeggy Sep 13 #1
John1956PA Sep 13 #2
CaliforniaPeggy Sep 13 #3
FiveGoodMen Sep 13 #4

Response to John1956PA (Original post)

Fri Sep 13, 2019, 02:39 AM

1. Looks like we're in for a rare, real treat!

I hope to have clear skies tomorrow night so I can get some photos.

Thank you for doing the arithmetic! I am lousy at that.

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Response to CaliforniaPeggy (Reply #1)

Fri Sep 13, 2019, 02:41 AM

2. You are welcome, Peggy. It is always nice to hear from you.

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Response to John1956PA (Reply #2)

Fri Sep 13, 2019, 02:52 AM

3. As soon as I saw you'd posted this, I wanted to respond! And that was easy.

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Response to John1956PA (Original post)

Fri Sep 13, 2019, 05:21 PM

4. So, it hasn't looked the same in all the intervening years?

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