You can change one of your availabilities by going to your calendar page.
You can make the following edits:
Changing a recurring availability
- Change the start time, end time or date for an instance and all future ones
- Change the start time, end time or date for just one instance (leaving all the other instances of that recurring availability unchanged)
- Delete an instance and all future ones
- Delete just one instance
Changing a single availability instance
- Change the start time, end time or date
- Make it repeat every week for that day
- Delete it
Note, you can not change or delete availability in the past.
If you want to learn more about setting your availability, then please read this article.