No, the landlord cannot in a residential rental agreement restrict the tenant from being able to give notice of termination mid-month, nor may the landlord prohibit the tenant from giving notice during certain months of the year.
If the rental property is located in the City and County of San Francisco, keep in mind that the San Francisco Rent Ordinance might also be in effect.
Frank W. Chen has been licensed to practice law in California since 1988. The information presented here is general in nature and is not intended, nor should be construed, as legal advice for a particular case. This posting does not create any attorney-client relationship with the author. For specific advice about your particular situation, consult with your own attorney.
Per your comment, yes, terms that contradict the law are void.
Keep in mind, however, that if you do give notice mid-month, your 30-day notice will terminate mid-month of the next month, meaning that your rent will likely have become due on the first or thereabout.
To avoid a 3-day Notice to Pay or Quit, you should pay the FULL month's rent and then request a reimbursement for the pro-rated half-month along with your security deposit. There might be an argument under CA Civil Code § 1946 that you only have to pay the half-month's rent, but then you leave yourself open to asserting that argument as a defendant in an Unlawful Detainer action based on the 3-Day Notice to Pay or Quit for failing to pay the full month's rent.
Kevin King, Principal- Essential Law Services. HTTP://ESSENTIALAW.COM, 415-562-6862. The information presented here is general in nature and is not intended and should not be construed as legal advice for a particular case. This post does not create any attorney-client relationship with the author of the question answered. For specific advice about your particular situation, consult with me or another qualified attorney off-site.