Cal. Probate Code § 3920.5

(a) Subject to the requirements and limitations of this section, the time for transfer to the minor of custodial property transferred under or pursuant to Section 3903, 3904, 3905, or 3906, may be delayed until a specified time after the time the minor attains the age of 18 years, which time shall be specified in the transfer pursuant to Section 3909. (b) To specify a delayed time for transfer to the minor of the custodial property, the words “as custodian for (Name of Minor) until age (Age for Delivery of Property to Minor) under the California Uniform Transfers to Minors Act”shall be substituted in substance for the words “as custodian for (Name of Minor) under the California Uniform Transfers to Minors Act” in making the transfer pursuant to Section 3909. (c) The time for transfer to the minor of custodial property transferred under or pursuant to Section 3903 or 3905 may be delayed under this section only if the governing will or trust or nomination provides in substance that the custodianship is to continue until the time the minor attains a specified age, which time may not be later than the time the minor attains 25 years of age, and in that case the governing will or trust or nomination shall determine the time to be specified in the transfer pursuant to Section 3909. (d) The time for transfer to the minor of custodial property transferred by the irrevocable exercise of a power of appointment under Section 3904 may be delayed under this section only if the transfer pursuant to Section 3909 provides in substance that the custodianship is to continue until the time the minor attains a specified age, which time may not be later than the time the minor attains 25 years of age. (e) The time for transfer to the minor of custodial property transferred by irrevocable gift under Section 3904 may be delayed under this section only if the transfer pursuant to Section 3909 provides in substance that the custodianship is to continue until the time the minor attains a specified age, which time may not be later than the time the minor attains 21 years of age. (f) The time for transfer to the minor of custodial property transferred by a trustee under Section 3906 may be delayed under this section only if the transfer pursuant to Section 3909 provides that the custodianship is to continue until a specified time not later than the time the minor attains 25 years of age or the time of termination of all present beneficial interests of the minor in the trust from which the custodial property was transferred, whichever is to occur first. (g) If the transfer pursuant to Section 3909 does not specify any age, the time for the transfer of the custodial property to the minor under Section 3920 is the time when the minor attains 18 years of age. (h) If the transfer pursuant to Section 3909 provides in substance that the duration of the custodianship is for a time longer than the maximum time permitted by this section for the duration of a custodianship created by that type of transfer, the custodianship shall be deemed to continue only until the time the minor attains the maximum age permitted by this section for the duration of a custodianship created by that type of transfer.