You may want to check the writ again. Writs in DC are issued for a seventy-five day period and during that period the eviction could take place on any weekday that the weather is above freezing and not raining or snowing. The landlord usually gets a day or two of notice that the Marshals are ready, so having a specific date set in May would be out of the ordinary. That doesn't mean your eviction will take place soon, the bad weather has created a backlog of evictions. However, regardless of any understandable frustration you may have with the delay, changing the locks is a bad idea. The tenant or the subtenant could come back and sue you for illegal eviction. Even of you have to wait a couple months for an eviction avoiding an illegal eviction is worth it and the only legal thing to do.