California Code, Labor Code - LAB § 751.8

(a) Notwithstanding Section 750, the period of employment may exceed eight hours in any 24-hour period if the employee is paid at the overtime rate of pay for hours worked in excess of that employee's regularly scheduled shift and for hours worked in excess of 40 hours in a seven-day period. Unless regularly scheduled shifts are established pursuant to Section 750.5, overtime rates of pay shall be paid for all hours worked in excess of those hours prescribed by Section 750 as the maximum allowable hours of employment.

(b) All work performed in any workday in excess of the scheduled hours established by an agreement pursuant to subdivision (b) of Section 750.5 up to and including 12 hours, or in excess of 40 hours in a workweek, shall be compensated at one and one-half times the employee's regular rate of compensation. All work performed in any workday in excess of 12 hours shall be compensated at double the employee's regular rate of compensation. No hours that are compensated at either one and one-half times, or double, the regular rate of compensation shall be included in determining the number of hours an employee has worked in a workweek for purposes of computing premium compensation.