CA Rev & Tax Code Section 11338

(a)

The owner or assessee may file a petition for reassessment on or before September 20. If the petition is not filed on or before September 20, or, if the period is extended by the board, by October 5, the assessment of the board shall be final.

(b)

The board may extend the period for filing a petition until October 5 provided a written request for the extension is filed with the board on or before September 20.

(c)

The board shall hear the applicant on such petition on or before January 31.