Setting Available Time Zones
The time zone setting works in conjunction with the local time element in the edit form of the CMS. When no time zones are configured in System Options, the local time element doesn’t have any time zone options available. When time zones are configured, time zone options are available.
To configure time zones, navigate to Administration > System Options > CMS > Time Zones. A list of available time zones appears in the edit pane.
Click the time zones you want to make available to users and then click Save. (Clicking Available Time Zones reorders the list.)