Work day and calendar availability are not always fixed and there are times where you need to be available or not available outside your regular schedule.
When those days arrive you can use the Date Specific Availability feature to better manage your calendar and business hours.
If there is a specific date you know you will have different hours, you can navigate to your Calendar and customize your availability under Edit Calendar > Additional Date-Specific Availability:
You can also change this in the calendar settings through Settings > Availability & calendar or per staff member under Settings > Staff > Edit staff member > My schedule in case you have a specific staff member that is traveling for work and is available on a different timezone:
If your schedule is more service specific, you can make the customization straight out of the service in questions through Settings > Services > Edit the relevant service if you have a specific date that you offer a very late or very early addition: