Downtime Scheduler Help

Here is the scenario we do monthly patching on a number of servers. Great ill setup a downtime schedule for these servers so we don't get needless alerts. Say the maintenance is scheduled for 2 hours and i setup a 2 hours downtime schedule. But since i'm such an efficient admin i actually finish in 1 hour and now i want to check my servers health and start monitoring again. There appears to be no way to Cancel the downtime once scheduled. If i try to disable the downtime i get the message "Unable to perform this action, Downtime scheduler is in running state" same if i try to delete it or modify it to change the end time. How can i cancel downtime if the maintenance is completed early?