Legal Question in Civil Litigation in California

Do not do this without an attorney, because otherwise you will lose and you will be stuck with the judgment. That said, you need to give sixteen court days (weekdays that aren't holidays) plus an additional five days if you serve the motion by mail.

If you hand serve it, the notice of motion AND all supporting papers must be filed and served at least 16 court days before the hearing. They must be served earlier if served by mail or over-night delivery service.

A motion must be filed no later than 16 court days prior to the hearing reserved on the motion. Court days means you don't count weekends and judicial holidays. You can get a list of judicial holidays from most court's websites.

The motion must be served at least 16 court days on your opponent, or their attorney of record. This time must be increased, depending on the manner in which the papers are served, as pointed out by Mr. McCormick. The rule regarding this is set forth in Code of Civil Procedure section 1005 subdivision (b).

Mr. Stone has a point that you should not go it alone. A motion to set aside a default has many picky rules. For example, you must submit as an exhibit your proposed answer, and that answer must state a defense. Some grounds for vacating a default are discretionary, meaning the court has the discretion to say no. There are also time limits on when you can file a valid motion to vacate the default, and any corresponding default judgment.