Since version 5.12.2 we have access to the Mercury API item that controls overrides. This is awesome for 2 reasons:
Please note, converting time zones no longer applies. Enter time normally.
Once inside the override box give the override a name, select "unlocked" for door mode, partition (your school), and select starting/ending time.
Please make sure to select a partition. If not selected all users in the access control manager (including ones from other schools) will be able to modify or delete your override!
Once an override is created it can be edited.