About Accounting for Daylight Saving Time Adjustments

If an event occurs during a time period when Daylight Saving Time (DST) begins or ends, and your plant exists in a part of the country where DST is observed, you will probably want to adjust the values in these fields to account for the DST adjustment.

For example, in 2007, DST in the United States started at 2:00 A.M. on March 11. As a result, observers of DST lost one hour of daylight (e.g., a clock that read 4:00 A.M. on March 11 would have read 3:00 A.M. on March 10). Because DST started at 2:00 A.M., observers were required to set their clocks forward one hour at that time. So at 2:00 A.M., you had to set your clock to 3:00 A.M. even though an hour had not actually passed.

With that in mind, suppose an event occurred at 11:00 P.M. on March 10, 2007 and ended at 4:00 A.M. on March 11, 2007. By the clock, it would appear that the event lasted five hours. In reality, the event lasted only four hours because DST added an hour to the clock even though that hour did not actually occur.

If you allow the GE Digital APM system to take DST into account, the calculations will account for power for the four hours that the event lasted according to real linear time. To do so, you must select the Use Daylight Saving Time check box in Plant datasheet.

If you do not allow the GE Digital APM system to take DST into account, the calculations will account for power for the five hours the event lasted according to the clock.