For purposes of this chapter, bonds, warrants, contracts, obligations, and evidences of indebtedness shall be deemed to be in existence upon their authorization. Bonds and warrants shall be deemed authorized as of the date of adoption by the governing body of the public agency of a resolution or ordinance authorizing their issuance, and contracts shall be deemed authorized as of the date of adoption by the governing body of the public agency of a resolution or ordinance approving the contract and authorizing its execution.