that'll be the day

Meaning: (originallyAustralia,New Zealand,idiomatic,informal)Saidinreplyto something that onebelieveswillneverhappen.Synonym:that'll be the frosty FridayI’m going to get into work on time today. —That’ll be the day!1990, Trent Christopher Ganino,Eric A. Stillwell, “Yesterday's Enterprise”, inStar Trek: The Next Generation, season 3, episode15, spoken byJean-Luc Picard(Patrick Stewart):Transmission from Klingon ship:Federation shipEnterprise.Surrender and prepare to be boarded. /Jean-Luc Picard (Patrick Stewart):That will be the day.

Examples:

EN: Now, that'll be the day.
ES: Ese será el día.
EN: Yeah, that'll be the day!
ES: Sí, fíate y verás.
EN: I mean, eh yes, that'll be the day!
ES: ¡Digo, eh sí, cómo se va a ir usted!
EN: Yes, kitten. But that'll be the day when you grasp that
ES: Sí, gatita. ¿Pero cuándo captarás el concepto?
EN: Oh, that'll be the day.
ES: Ni soñando
EN: But that'll be the day when you grasp that
ES: Pero ¿Cuándo captarás el concepto?
EN: Yeah, that'll be the day alright.
ES: Sí, habría que verlo.
EN: You know, the day we get treated half as good as our horses, that'll be the day.
ES: El día que nos traten tan bien como a los caballos será nuestro día.
EN: Oh, that'll be the day, won't it?
ES: Oh, cuándo será eso ¿no?
EN: God, a Puerto Rican steambath attendant, boy, that'll be the day.
ES: ¡Dios, un puertorriqueño en un baño de vapor!
EN: ♪ Well, that'll be the day when you say goodbye
ES: #Eso habrá que verlo, que me digas adiós.#
EN: ♪ Well, that'll be the day when you say good-bye ♪ ♪ That'll be the day when you make me cry ♪
ES: Well, that'll be the day, when you say goodbye that'll be the day, when you make me cry
ES: Well, that'll be the day, when you say goodbye that'll be the day, when you make me cry
ES: Well, that'll be the day, when you say goodbye that'll be the day, when you make me cry
ES: Well, that'll be the day, when you say goodbye that'll be the day, when you make me cry
EN: ♪ 'Cause that'll be the day when I die ♪
ES: Cause that'll be the day when I die
ES: Cause that'll be the day when I die
ES: Cause that'll be the day when I die
ES: Cause that'll be the day when I die
ES: Cause that'll be the day when I die
EN: ♪ Well, that'll be the day ♪
ES: Well, that'll be the day, hoo-hoo
EN: ♪ Well, that'll be the day.
ES: I Bien que será el día...

Note: the examples for non latin scripts have a high likelihood of mistakes, we do not own any of this data and it is sourced from Wiktionary, the NLLB database and Opensubtitles. Please help us improve this by contributing correct examples. We will be working to fix this issue over time however it is a bigger issue due to the the difficulties in dealing with non latin scripts and grammatical structures(non-romantic/european languages have lower resources as well ).