Our finals schedule is also printed in the class schedule at enrollment time so students know the date and time of finals for each class period.  I usually teach several sections of business law each semester.  I announce the finals date and time for all my sections in each class, and tell students that they may take the final at any of those times, but only at those times.  I have never had a student request a makeup final, but would probably allow one, given a "good" excuse, such as a death in the family verified by obituary, etc.  I allow makeups for other tests during the semester for similar reasons, but students know that they will be taking a different version with more difficult questions, so not too many take advantage of this.