April Fools’ Day usually finishes at 12 noon on April 1 in many places, though some people treat it as lasting the full day.

Quick answer

If you’re going by the common tradition, the pranks stop at midday.

Why people say noon

A lot of guides and etiquette references describe 12:00 noon as the cutoff for April Fools’ jokes.

That said, the rule isn’t universal, and some people still joke until the end of the day.

In plain terms

  • Traditional cutoff: noon on April 1.
  • More relaxed view: the whole day can count.
  • Best practice: keep jokes harmless and stop once they stop being funny.

If you want, I can also tell you why noon became the usual cutoff.