I would like to know if someone could provide me some examples of the usage of those phrases?
closed as not a real question by tchrist, Kris, Matt E. Эллен♦, Mahnax, waiwai933♦ Aug 23 '12 at 23:20
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They're both proper English, and they mean different things.
no joke this time implies that one is being serious: what was just said (or about to be said) should not be taken as a joke.
no jokes this time is more of a command: to stop joking around and be serious: