Defamation: Whtt is the Statute of Limitations for Defamation

My question involves defamation in the state of: California

Is there a statute of limitations for defamation? If I continue to protest - politely, legally - how long can they bring up the old threat to sue over prior comments/posts?

I know it doesn't matter... but everything thing that they say is defamation IS TRUE. I can't prove it and they have their employees to contradict my one voice.

Defamation: Whtt is the Statute of Limitations for Defamation