Time zone settings in Users individual Preferences override the Global Default Preferences. Please note that modifications do not take effect until the next logon session.
Modifying individual users Time Zone preferences:
This will need to be done to each account that is effected.
1) Login as the effected user
2) Navigate to:
2.x: Policy > Manage Passwords > Preferences (top right)
3.x: <Users Real Name > (on top right, near logout) > Preferences
3) Modify "Time Zone Region"
Modifying PAM Default Time Zone:
1) Navigate to:
2.x: Policy > Manage Passwords > Settings > UI Settings
3.x: Settings > Global Settings > Default Preferences
2) Modify "Time Zone Region"