Cal. Gov. Code § 32365

If, after the effective date of this section a member who retired at any time after January 1, 1945, pays into the fund the difference between what he did contribute and what he would have contributed had Section 32322 always read as it now reads, and also pays the interest which would have been accrued upon such difference, then upon such payment, all retirement payments made subsequent to such payment shall be calculated as if such member had retired subsequent to the effective date of this section.