Short answer. Thirty calendar days. Rule 11, Section 1 of the Rules of Court requires the defendant to file an answer to the complaint within thirty calendar days after service of summons, unless a different period is fixed by the court. The count runs from service of summons, not from the date the case was filed.
What the law says
The defendant shall file his or her answer to the complaint within thirty calendar days after service of summons, unless a different period is fixed by the court.
Rule 11, Section 1 — Answer to the complaint. Read the full provision →
The thirty days and where they start
Section 1 states the whole rule in one sentence: The defendant shall file his or her answer to the complaint within thirty calendar days after service of summons, unless a different period is fixed by the court. The trigger is service of summons — the day the case was filed is irrelevant to your deadline, and so is the day you informally learned that a case existed. And the Rules say calendar days: weekends and holidays inside the period are counted, not skipped, so the thirty days runs shorter in working time than it sounds.
The court can fix a different period
The tail of the sentence matters as much as the number: unless a different period is fixed by the court. Thirty days is the default, not a constant. The summons itself and any accompanying order are where a different period would appear, which is why the first task on being served is to read every page of what the process server handed over, note the date of service in writing, and calculate the deadline from the documents rather than from assumption. If the court fixed a different period, that period — not the familiar thirty — is the one that binds.
Why the deadline is not decorative
A defendant who lets the period pass without filing an answer surrenders the one chance the Rules give to put denials and defences on record at the start, and the case does not wait — procedure supplies the plaintiff with remedies against a defendant who stays silent, and none of them improve with time. Whatever you think of the complaint's merits, the thirty days is the window in which thinking must turn into a filed pleading. Treat the service date as the start of a countdown, because that is exactly what the section makes it.
Use the period like the working month it is
An answer is more than a denial: it is where a defendant's version of events, defences, and any claims back against the plaintiff enter the case, and assembling that — contracts, receipts, correspondence, the names of the people who know the facts — takes most defendants far longer than they expect. Bring the summons, the complaint and all its annexes to a lawyer early in the period, not in its final days; a well-built answer filed on day twenty-five beats a rushed one filed at the wire.