[[Another person stuck in a Sisyphean thought bubble.]]
Person 1: ((thinking)) Thirty days hath September, April, June and November.  All the rest have 31- except February, which has 28, and leap year which makes it 29.  
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Wait, which month was I listening for? Oh right, October.
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Did I say "October" in there? Now i can't remember.
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30 days hath September...

{{Title text: There's a cool mental calculation hack I recently learned for this: If you open the calendar app on your phone or computer, the highest-numbered box along the bottom is equal to the number of days in the month!}}