You can schedule a sales tier to start and end in advance or have it start immediately.
Start Now - By selecting this option, the sales will start immediately upon creation.
Schedule start date time - By selecting this option, you can schedule the sales to start in advance by selecting the date and time.
The date and time is based on your store's timezone.
Set end date - By selecting this option you can schedule in advance when the sales when end will end.
You can use it with Start Now option as well:
When the discount tier reaches the end date it will be automatically deactivated
Should you wish to activate an expired pricing tier, you are required to reschedule the pricing tier again: