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A theory used by measuring the number of days in a month. If your index finger touches your knuckle of your hands, the month has 31 days, while if you touch the skin of your fist, it has 30 (with the exception of February).
Scott: Dude, how many days are there in August?

Dave: 31.

Scott: Isn't it 30?

Dave: Use the Knuckle Theory.
by OpeN333 October 22, 2013
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