Cal. Code Regs. tit. 18, § 13403.2 – Rates Applicable to Transfers Inter Vivos.

(a) On or After June 25, 1935. Where property was transferred during the life of the transferor on or after June 25, 1935 (the effective date of the Inheritance Tax Act of 1935), the rates of taxation applicable are those in effect at the date of the transferor's death.
(b) Prior to June 25, 1935. Where property was transferred during the life of the transferor prior to June 25, 1935, the rates of taxation applicable are:
1. (1) Those in effect at the date of the transfer, if the transfer was complete, see Section 13304.1; or
2. (2) Those in effect at the date of the transferor's death, if the transfer was incomplete, see Section 13304.2.
  Note: Reference: Section 13403, Revenue and Taxation Code.