California Code, Code of Civil Procedure - CCP § 208

The jury commissioner shall estimate the number of prospective jurors that may be required to serve the needs of the court, and shall summon prospective jurors for service. Prospective jurors shall be summoned by mailing a summons by first-class mail or by personal service or, in urgency situations, as elsewhere provided by law. The summons, when served by mail, shall be mailed at least 10 days prior to the date of required appearance. Once a prospective juror has been summoned, the date, time, or place of appearance may be modified or further specified by the jury commissioner, by means of written, telegraphic, telephonic, or direct oral communication with the prospective juror.