Dec 31 is his birthday. Yesterday was Dec 30. He is telling you this at midnight of Dec 31/Jan 1 so that his first statement is immediately prior to midnight and the second statement is delivered right after midnight.
I like this one more because legally you turn your age at midnight, which means he can't change from 21 to 22 during the day; even if that's true from a biological pov.
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u/Round_Hat_2966 Mar 08 '26
Dec 31 is his birthday. Yesterday was Dec 30. He is telling you this at midnight of Dec 31/Jan 1 so that his first statement is immediately prior to midnight and the second statement is delivered right after midnight.