that'll be the day

== English == === Etymology === Originally referring to a significant day in the future regarded as worth waiting for. === Pronunciation === (Received Pronunciation) IPA(key): /ˌðætl̩ biː ðə ˈdeɪ/ (General American) IPA(key): /ˌðætl̩ bi ðə ˈdeɪ/ === Phrase === that'll be the day (originally Australia, New Zealand, idiomatic, informal) Said in reply to something that one believes will never happen. Synonym: that'll be the frosty Friday ==== Translations ==== ==== See also ==== a cold day in hell a week from next Tuesday until the cows come home when hell freezes over when pigs fly === References ===