From
http://www.leginfo.ca.gov/cgi-bin/di...&file=818-827:
827. (a) Except as provided in subdivision (b), in all leases of
lands or tenements, or of any interest therein, from week to week,
month to month, or other period less than a month, the landlord may,
upon giving notice in writing to the tenant, in the manner prescribed
by Section 1162 of the Code of Civil Procedure, change the terms of
the lease to take effect[...]; provided,however, that it shall be
competent for the parties to provide by anagreement in writing that
a notice changing the terms thereof may be given at any time not less
than seven days before the expiration of a term, to be effective upon
the expiration of the term.
From CA law it looks like they need to inform you 7+ days before the lease ends to make a change that takes effect when the lease ends. I'm no lawyer, but I've had some luck printing out and reminding landlords how local tenant law works. Most of them simply don't want the legal hassle.