Cal. PROB § 16376

(a) A fiduciary shall allocate an income receipt or disbursement, other than a receipt to which subdivision (b) of Section 16370 applies, to principal if its due date occurs before the date on which either of the following occurs:

(1) For an estate, the decedent died.

(2) For a trust or successive interest, an income interest begins.

(b) If the due date of a periodic income receipt or disbursement occurs on or after the date on which a decedent died or an income interest begins, a fiduciary shall allocate the receipt or disbursement to income.

(c) If an income receipt or disbursement is not periodic or has no due date, a fiduciary shall treat the receipt or disbursement under this section as accruing from day to day. The fiduciary shall allocate to principal the portion of the receipt or disbursement accruing before the date on which a decedent died or an income interest begins, and to income the balance.

(d) A receipt or disbursement is periodic under subdivisions (b) and (c) under either of the following circumstances:

(1) The receipt or disbursement shall be paid at regular intervals under an obligation to make payments.

(2) The payor customarily makes payments at regular intervals.

(e) An item of income or obligation is due under this section on the date the payor is required to make a payment. If a payment date is not stated, there is no due date.

(f) Distributions to shareholders or other owners from an entity to which Section 16340 applies are due at one of the following times:

(1) On the date fixed by or on behalf of the entity for determining the persons entitled to receive the distribution.

(2) If a date is not fixed, on the date of the decision by or on behalf of the entity to make the distribution.

(3) If a date is not fixed and the fiduciary does not know the date of the decision by or on behalf of the entity to make the distribution, on the date the fiduciary learns of the decision.