I’ve seen both and never been sure if one was more old fashioned or less “courant” than the other.

3 Answers 3


In text documents, un de ces jours is much more common, even when including un de ces quatre in the comparison :

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Un de ces quatre, being more colloquial, is certainly more frequent in spoken French than in books, but I believe un de ces jours still leads in this context although I have no data to back it up.

  • Note that "un de ces quatre" is significantly more common than the full "un de ces quatre matins" variant. Also that Google ngrams only accounts for occurences in books. May 26, 2018 at 23:26
  • @StéphaneGimenez Indeed. Answer updated. Thanks.
    – jlliagre
    May 27, 2018 at 7:20

"A un de ces quatre (matins)" is only used with good friends. While "A un de ces jours" can be said to anyone.


Tu le reverras "un de ces quatre (matins)" est plus familier et "un de ces quatre" encore plus. "A un de ces jours!", c'est pour ne pas dire "Au revoir!"

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