Your weekly availability is defined in the time zone set for your booking schedule. A booker sees the same appointment in their own local time zone. The confirmation email and calendar invitation use the time zone associated with the recipient.
When comparing times with a customer, include the time zone rather than sending a time alone. This is especially important when you are in different countries or when one of you has recently changed clocks for daylight saving time.
If a time looks different in an email, calendar or booking page, check the time zone shown alongside it before changing the appointment. See Manage appointments.