Legal Question in Criminal Law in California

Probably a "reasonable" time which is going to vary depending upon the circumstances. The warrant itself might state a time limit.

With all due respect to the previous answer, it is dead wrong.

Search warrants expire 10 days after signed by the judge. If they do not serve it within that time, they must get a new warrant or "refresh" the expired one, but it takes a judge to authorize either.

If you're asking about arrest warrants, then the answer is never. Arrest warrants don't expire and will remain active until served or recalled by the court that issued it.

I agree with Mr. Dane. A search warrant must be executed within 10 days of the date it bears and after the ten days it because void and valueless. (Pen. Code, sect. 1534.)