When you use the Make multiple changes tool for campaigns or sitelinks, include an "Ad schedule" column to add, change, or remove schedules.
Here's a sample campaign list, where the first line is a column header row:
Campaign, Ad schedule
Campaign #3, (Tuesday[10:00-14:00])
Campaign #2, 
In this example, Campaign #3 will start running on the specified schedule (Tuesdays from 10 am to 2 pm), and any current ad schedules for Campaign #2 will be turned off.
|"Ad schedule" column value||Result|
|(Day[time-time])||Enable the specified ad schedule.
See formatting instrucions.
|[ ]||Remove existing ad schedules.|
|Leave column blank.||No changes.|