You can find the fields for setting a cut-off in the "Events" tab, under "The Basics". From here, look under the "Event Dates" sub-heading and set what date and time you want cut-off to go into effect. Note that the hour drop-down is written in a 24-hour clock format, meaning for example "Hour 17" means 5:00 PM, and "Hour 0" means 12:00 AM.

But wait, there's more! Click here for information about event hotel cut-off dates, or here for sub-block cut-off dates.