Allowing the selection of time zone
Time zones and daylight savings time (DST) affect time stamps. Users expect to see information displayed in their own time. If a user located in Japan or Australia generates a transaction on a U.S.-based server, the time stamp must be adjusted to meet the user's expectations.
Example: The United States Congress recently passed the Energy Policy Act of 2005 that changes the start and end dates of DST in the United States starting in 2007. Other countries are also planning to change their DST rules to stay in sync with the U.S. This change will affect all date and time processing functions in a computer such as calendaring, scheduling and date manipulation functions.