California Code, Government Code - GOV § 29824

(a) The rate of interest payable on a registered warrant shall be determined by a ratesetting committee upon the affirmative vote of a majority of its members.  A ratesetting committee shall consist of the auditor, the treasurer, and one representative of the issuing local agency, and shall in its discretion set a rate of interest payable on registered warrants that is consistent with sound business principles.

(b) Interest on registered warrants shall be paid on the basis of actual days and a 365-day year, and shall accrue to the holder of the warrant on the date of redemption.  A registered warrant shall cease to bear interest on any maturity date endorsed on its face, if on that date unapplied money is available for its payment, or on the date of the treasurer's notice pursuant to subdivision (b) of Section 29826.