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Example of UTC Data Conversion

This topic is part of About Global Time Zone and Universal Time Coordinated (UTC).

To illustrate how UTC data conversion works, suppose a scenario where User 1 is in New York, User 2 is in San Francisco, and the database server and the Siebel Server are in Utah. Today's date is November 20th. The time zone for User 1 is equivalent to UTC minus 5 (Eastern Standard Time), and the time zone for User 2 is equivalent to UTC minus 8 (Pacific Standard Time).

User 1 logs in and books a meeting with User 2. User 1 sets the meeting for December 15, 1 pm New York time, which is UTC minus 5. The time stored in the database is changed by the Application Object Manager component on the Siebel Server before storage by applying this user's time zone offset, UTC minus 5, to the local time value. So the meeting time stored is 1 pm (EST) plus 5 hours, which is 6 pm UTC (1800 in 24-hour clock time, which is what is actually stored).

Note that because the meeting date is in December, and because the date when the users are viewing the meeting is in November, standard time applies and no adjustments for daylight savings time (DST) are necessary.

User 2 (in San Francisco) now looks at her calendar. She sees the time for the meeting as 10 am. The Application Object Manager has read the value of 1800 from the database and applied her time zone offset, UTC minus 8, to this value. 1800 minus 8 hours is 10 am (PST).

The described time-zone handling behavior can be generalized as follows:

• For a time zone offset like UTC minus x, the value x is added to a local time value to get the UTC time value for storage, or is subtracted from a UTC value to get the local time for display to a user.
• For a time zone offset like UTC plus x, the value x is subtracted from a local time value to get the UTC time value for storage, or is added to a UTC value to get the local time for display to a user.