if he's, she's, etc. a day

if (one) is a day

Used to emphasize that one must be a certain age. How does he keep himself looking so young—he's got to be 60 if he's a day!
See also: if
Farlex Dictionary of Idioms. © 2015 Farlex, Inc, all rights reserved.

ˌif he’s, she’s, etc. a ˈday

(informal) (used when talking about somebody’s age) at least: She isn’t forty! She’s fifty-five if she’s a day!
See also: if
Farlex Partner Idioms Dictionary © Farlex 2017
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