I've encountered a big corporate landlord in West Campus, Austin, Texas, that's only willing to reassign the lease at the start of a month, saying that they don't prorate rents.
(Interestingly enough, all of their original leases are from mid-August to end of July, with 12 equal instalments.)
If someone is done with classes mid-May, and wants to sublet to someone else for the summer session, would it be legal for a Texas landlord to deny a sublet from mid-May, and require that the reassignment be from June 1 instead?