21 Day Security Deposit Refund

[Josh Epstein]

As a landlord in California, do I have to return the tenant's security deposit within 21 days if the tenant broke their lease? The tenant's lease was through December 31st 2016. They moved out on December 10th and paid through December 10th.  I was able to re-rent the unit on December 24th. I deducted the cleaning fees from their deposit and only deducted the days that were not rented (13 days). They received this refund on January 7th and they are asking for their entire deposit back since their refund was received 28 days after they moved out, not 21 days. They are referencing California code 1950.5 but that seems applicable only if a tenant satisfies the lease.  What is my legal right as a landlord?

Thank you in advance!