Just type some type of letter reminding them of the last day when they have to surrender the keys.

I would charge them rent for the entire month of February if they were not out.In the future, consider a lease clause like this:TENANT HOLDOVER: If you or any occupants that were allowed access by you remain in possession of the Premises after the termination of this lease, you agree to pay a holdover fee at the daily rental rate (current monthly rent divided by 30) plus $10 for each day the rental unit is not legally surrendered.

I know in Colorado 91 days notice of date to surrender unit  is required to terminate lease if any notice is required by lease.

If Tenant(s) abandon or surrender the premises at anytime and leaves personal property there, Agent may dispose of it however Agent chooses, and Tenant shall reimburse Agent for all costs incurred in that regard.Full-disclosure that I have yet to be in a situation where I've needed to enforce that, so TBD how it plays out in practice.

The mortgage - note holder must surrender the title to the Dept. of revenue in order to attach the MH to the land nowdays.

Hopefully after the enormous surrender time has passed. 

Summaries include disciplinary actions initiated against real estate licensees; orders to desist and refrain from unlawful activities; decisions on petition applications to reinstate/remove restrictions from licensees; applications for licenses that have been denied and/or were issued restricted licenses; and licenses that have been voluntarily surrendered.

When I was looking for a shelter dog, the county shelter was 98% pit bulls that were wound up like crazy, and likely surrendered because the landlord wouldn't allow a dog.  

The money is disbursed from escrow as follows: Rent until seller surrenders possession plus damages discovered at move out.

We never had a referendum, we never surrendered these rights, it was imposed without recourse or means to address grievances thereof.