You don’t need to do the math
Time zones are handled automatically. You set your hours once, in your own time zone, and the Calendar shows every visitor the same times translated into their own time zone.
Screenshot coming soon
Your time zone
Set it in Calendar → Settings.
Every availability rule you create (e.g. "Monday 9:00–17:00") is stored in this time zone.
All confirmation emails to you are written in this time zone.
Your visitor’s time zone
When someone opens your booking page, their browser’s time zone is detected automatically.
They can change it from a dropdown at the top of the page if they are travelling.
The available slots are shown in their time. The slot they pick is sent to you in your time.
Example
You are in Berlin and your hours are 9:00–17:00. A visitor in New York opens your link. They see slots between 3:00 AM and 11:00 AM (their time), which matches your 9:00–17:00 Berlin time. They pick 4:00 PM their time. In your dashboard and inbox, you see 22:00 Berlin time — and you can decide whether that fits.
Daylight Saving Time
Time zone changes (summer/winter time) are handled automatically. If your country switches on a Sunday, your bookings on the Monday after will still show at the correct local time on both sides.
The confirmation email
Both you and the visitor get an email with an .ics calendar invite. The invite contains the absolute time, so it always appears at the correct local time in whichever calendar app you use (Apple Calendar, Google Calendar, Outlook…).