What is the statute of limitations for challenging an election in a California general law city?

I'm working with some people who want to challenge an assessment election that occurred a couple of months ago. How long do they have to challenge the results?

Public Comments

1. Challenge it on what basis? It appears that the time to do so has expired. See California Elections Code 15620 through 15634 at: http://caselaw.lp.findlaw.com/cacodes/elec/15620-15634.html