TimeDive picks up the timezone based on the device's setting and will add it to the profile.
However, you can still change the timezone of the employee.
Here's how you can do that:
Open the profile of the employee from the directory tab
Select the timezone from the dropdown menu and hit Update.
Note:
If you want to restrict your employees from making any edits to their profile, just toggle on the setting "Lock editing of the punches by non-admins" under the time tracking settings.