Time Zones, Order of Precedence in Siebel
A time zone is a region on Earth that has a uniform, legally mandated standard time.
Almost all time zones on land have legally defined borders which coincide with the borders of the country mandating the time or some subdivision thereof. Of the 40 time zones on land, most are offset from Coordinated Universal Time (UTC) by a whole number of hours (UTC−12 to UTC+14), but a few are offset by 30 or 45 minutes from a nearby hourly zone.
In Siebel Application TimeZones can be set at 3 different levels:
a). Database Server level Time zone
Control Panel -> Date and Time -> Time zone
b). Application Server level Time Zone
Application Administration -> System Preferences -> Default Time zone
c). User level Time zone
Site Map -> User Preferences -> Profile -> Time Zone
NOTE: Order of Precedence taken by Siebel for all Date and Time calculation is c > b > a.