The time zone setting applies to all messengers in your account and will be used to format the timestamp for messages displayed in the message history page, google maps popup and the timestamp sent in email notifications to your contact list. (*note that the timestamp is not included in notifications sent to mobile contacts.) When making updates to the time zone, the change will be immediate for the message and map display screens. However, it may take up to 4 hours for the time zone adjustment to be made in your outgoing Check-In & Help email messages.
At this time, pre-existing accounts will have their time zone setting defaulted to GMT.
To update this setting for your account, click on the "Preference" link under the top level "Account" tab. When you select a country or territory the appropriate time zones can then be selected. When you are done, make sure you save your selection by hitting the "Update" button.
On shared pages, time is displayed per the user's computer time setting.