To edit an existing registration timeline, go to Settings >> Registrations >> click 'Edit' button next to timeline.
From here, you will be able to edit all registration timelines settings:
Registrations open - How far in advance can customers register? Use this setting to prevent customers from registering for classes too far into the future.
Registrations close - When can customers no longer register for a class? This cutoff can be before or after the class begins.
Cancellation cutoff - Cancellations after this cutoff will be late cancellations and will not be refunded.
Class types this registration time is applicable for.
Once you've finished editing, click 'Save'.