How do you design a system which can support multiple time zones?

Automatic time zone detection: The customer's time zone is detected automatically based on the computer's IP address. This means that if a customer travels to a location with a different time zone, they will be alerted of the time zone change and will be able to switch to the new time zone with one click.

fot more information click on the link: help.scheduleonce.com/customer/portal/articles/79635-our-time-zone-support