A time trigger is useful if you want to promote records for a particular period of time.
You specify a time trigger on the Time Trigger tab of the Rule editor. A time specified on this tab is a date/time value that indicates the time at which the rule may fire and the time after which the rule may not fire. Any matching query that occurs between these two values fires the rule.
For example, you might create a rule called This Weekend Only Sale whose time trigger starts Friday at midnight and expires on Sunday at 6 p.m. Only a start time is required for a time trigger. If you do not specify an expiration time, the rule can be triggered indefinitely.
To specify a time trigger:
The start time and expiration time values do not specify time zones. The server clock that runs your Web application identifies the time zone for the start and expiration times. If your application is distributed on multiple severs, you must synchronize the server clocks to ensure the time triggers are coordinated.