If you want the changes to go into effect the same day, make sure to toggle on the "Publish to today" option, then click "Publish schedule"\
\
Side note: publishing to today may cause your reservations on other days to be disrupted and moved around, so once you publish, make sure to review the next month or so to ensure it didn't cause any table movements (most commonly it will unassign large parties from their multi-table configuration, so you'll want to make sure those are reassigned so it doesn't leave open tables that are actually booked up)