if one is a day

• if a day, if one's a day

(This etymology is missing or incomplete. Please add to it, or discuss it at the Etymology scriptorium.)

if one is a day

1. If not older; at least.

   Antonym: at most

   He must be fifty if he's a day.

• not look a day over

• “if one is a day”, in Lexico, Dictionary.com; Oxford University Press, 2019–2022.
• “if one is a day” in Longman Dictionary of Contemporary English, Longman.
• “if one is a day”, in Merriam-Webster Online Dictionary, Springfield, Mass.: Merriam-Webster, 1996–present.
• “if someone s a day” (US) / “if someone s a day” (UK) in Macmillan English Dictionary.