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The CA Automation Point Enable Clock Change field in the Rules Settings dialog determines whether previously executed time rules reexecute after a backward time change.
In CA Automation Point, time rule logic becomes complex when a workstation's clock is changed during a normal Evaluation Frequency interval, such as the one-hour fall back change that occurs when switching the clock from daylight savings time to standard time, or the one-hour move ahead change that occurs when switching from standard time to daylight savings time. The move ahead change works in the same manner as if you had set the Evaluation Frequency interval to one hour—all rules in the one-hour range execute, with the same exception that was described previously when midnight is crossed. In this instance, only the rules from midnight to the end of the interval execute.
By default, CA Automation Point interprets a fall back change to actually be a move forward by 23 hours. When 02:00 is set back to 01:00 during an Evaluation Frequency interval, CA Automation Point views the time as moving forward 23 hours, across midnight. In this example, all rules from 02:00 to 23:59 are bypassed (not executed) and all rules from 00:00 to 01:00 are executed. As the time moves forward, all rules continue to execute normally, including those that executed the first time the clock advanced from 01:00 to 02:00. (Remember, because of the fall back change, the clock advances from 01:00 to 02:00 twice that day.) While CA Automation Point internally views this as a move forward by 23 hours, you will see that the rules between 00:00 and 02:00 executed twice (or reexecuted) on that day; because CA Automation Point does not associate a date with rules logic.
The primary purpose of enabling clock change is to allow you to determine how you want to handle fall back changes. Additionally, you can use this setting to address any backward time resets of up to two hours.
When the Enable Clock Change box is unchecked and the time is set back two hours or less, any previously executed rules within the time range from the backward reset time to the time the clock was prior to being set back will not reexecute. The rules resume normal execution when the time reaches the exact time at which the clock was set back. For example, if the clock is set back from 02:00 to 01:00, the rules do not resume executing until 02:00 is reached again. The rules behave this way even when the set back occurs across midnight, as long as the time difference is two hours or less. For example, if the clock is set back from 00:30 to 23:30 (which, when the Enable Clock Change box is unchecked, CA Automation Point interprets as a one-hour backward reset), no rules execute until the time reaches 00:30.
When the Enable Clock Change box is checked or the time is set back more than two hours, CA Automation Point assumes that the time moved forward. This logic works in the same manner described previously. If the move forward does not cross midnight, all rules in the range execute. For example, if the clock is set back from 02:00 to 23:00, CA Automation Point assumes that the clock moved forward 21 hours and that all rules from 02:00 to 23:00 executed. If the move forward crosses midnight, only the rules from midnight to the end of the interval execute. If the clock is changed from 06:00 back to 03:00, CA Automation Point assumes that the clock moved forward and crossed midnight. The rules from 06:00 to 23:59 are bypassed (not executed), while the rules from 00:00 to 03:00 are executed.
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