California Code, Health and Safety Code - HSC § 9024

(a) Except as provided in subdivision (b) of this section, subdivision (c) of Section 9023, and subdivision (d) of Section 9026, the term of office for a member of the board of trustees shall be for a term of four years and until the appointment and qualification of the successor. Terms of office commence at noon on the first Monday in January.

(b) For districts formed before January 1, 2004, where the members of the board of trustees are not serving staggered terms, the board of supervisors shall stagger the terms of the trustees and to accomplish this purpose shall appoint trustees, on or after January 1, 2004, for terms of less than four years. However, a board of supervisors shall not reduce the term of office of a trustee once the trustee has been appointed to that term, whether the appointment was made before, on, or after January 1, 2004.

(c) Any vacancy in the office of a member appointed to a board of trustees shall be filled promptly pursuant to Section 1779 of the Government Code. Any person appointed to fill a vacant office shall fill the balance of the unexpired term.