Cal. Civ. Code § 2981.7

All contracts entered into between a buyer and a seller on or after January 1, 1983, shall provide for the calculation of the finance charge contemplated by item (A) of paragraph (1) of subdivision (j) of Section 2982 on the simple-interest basis, if the date on which the final installment is due, according to the original terms of the contract, is more than 62 months after the date of the contract.