GOV § 64826

Any action to determine the validity of any tax, fee, or other charge provided for in, or the validity of bonds issued pursuant to, this title, or any of the proceedings, contracts, agreements, or other arrangements or matters entered into, shall be commenced within 60 days from date of the election or the adoption of the resolution approving those matters, as applicable, pursuant to Chapter 9 (commencing with Section 860) of Title 10 of Part 2 of the Code of Civil Procedure. After that date, the adoption of that tax, fee, or other charge, the issuance of the bonds, and all proceedings in relation thereto, shall be held valid and incontestable in every respect.