California Code, Probate Code - PROB § 21525

(a) If an instrument that makes a marital deduction gift includes a condition that the transferor's spouse survive the transferor by a period that exceeds or may exceed six months, other than a condition described in subdivision (b), the condition shall be limited to six months as applied to the marital deduction gift.

(b) If an instrument that makes a marital deduction gift includes a condition that the transferor's spouse survive a common disaster that results in the death of the transferor, the condition shall be limited to the time of the final audit of the federal estate tax return for the transferor's estate, if any, as applied to the marital deduction gift.

(c) The amendment of subdivision (a) made by Chapter 113 of the Statutes of 1988 is declaratory of, and not a change in, either existing law or former Section 1036 (repealed by Chapter 923 of the Statutes of 1987).