Short answer. Five calendar days from receipt, for a litigious motion. The Rules of Court direct that the opposing party shall file his or her opposition to a litigious motion within five calendar days from receipt thereof — and warn that no other submissions shall be considered by the court in resolving it.
What the law says
The opposing party shall file his or her opposition to a litigious motion within five calendar days from receipt thereof. No other submissions shall be considered by the court in the resolution of the motion.
Rule 15, Section 5 — Litigious motions. Read the full provision →
Five calendar days — counted from receipt
Two features of the deadline deserve emphasis. It is counted in calendar days, so weekends and holidays are included in the count, and it runs from receipt of the motion, not from the date the motion was filed or signed. That is why the rule takes service seriously: motions must be served by personal service, accredited private courier or registered mail, or electronic means so as to ensure their receipt by the other party. The moment a motion against you actually reaches you or your counsel, the five-day clock starts. Record that date — it is the anchor of everything that follows.
Which motions this covers
The five-day opposition period applies to litigious motions — those that can affect the other party's rights and therefore call for a hearing of both sides on paper. The rule lists them: a motion to dismiss, a motion for reconsideration or new trial, a motion for a bill of particulars, a motion for execution pending appeal, a motion to amend after a responsive pleading has been filed, a motion for intervention, a motion for judgment on the pleadings or summary judgment, a demurrer to evidence, a motion to declare the defendant in default, and other similar motions. The list ends open-endedly on purpose: if a motion seeks relief that could prejudice you, treat it as litigious and oppose it within five days.
One shot, then resolution
The rule is built for speed, and it closes the door after your opposition: No other submissions shall be considered by the court in the resolution of the motion. There is no reply to the opposition, no rejoinder, no supplemental round — the motion and the opposition are the whole record. The court must then act quickly: the motion shall be resolved by the court within fifteen calendar days from its receipt of the opposition thereto, or upon expiration of the period to file such opposition. Miss your five days and the court may resolve the motion on the movant's papers alone.
Making the five days count
Because the opposition is your only submission, it has to carry your entire case against the motion: every factual point, every legal argument, every annex. Do not hold anything back for a later pleading that the rule will not allow. If a motion reaches you directly and you have a lawyer, transmit it the same day, since counsel may have received it separately and the earlier receipt may control. And if you are the movant, serve the motion by a mode that proves receipt — the opposing party's five days, and the court's fifteen, are both measured from dates you will need to establish.