if (one) is 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.

if he (or she) is a day

at least (added to a statement about the age of a person or thing).
1992 Shashi Tharoor Show Business Lawrence must be fifty if he's a day.
See also: he, if
Farlex Partner Idioms Dictionary

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
See also:
  • if he is a day
  • if he's, she's, etc. a day
  • if one’s a day
  • if (one's) a day
  • if a day
  • be going great guns
  • gooseberry
  • green as a gooseberry
  • be (as) green as a gooseberry
  • French leave