Issue
Daylight Savings Time changeover may not automatically occur on some Network 8000 controllers.
Environment
Network 8000
Cause
The controllers with the "Formula Date" option selected will use the "Formula Date" information to calculate a Spring and Fall fixed date which is used to determine when the daylight savings changeover should occur. The fixed dates calculated will be for the current calendar year. This means that if a "Formula Date" recalculation is triggered on April 15, 2007 in a NW8000 controller, the controller will generate fixed dates of March 11, 2007 and November 4, 2007 corresponding to the 2nd Sunday in March and the first Sunday in November. Once the fall back date of November 4, 2007 has been processed, the NW8000 controller will not recalculate the new fixed dates for year 2008 until there is a trigger event that occurs after January 1, 2008. If no trigger event occurs between January 1, 2008 and March 9, 2008, the "spring ahead changeover" does not occur since the controller is still using the fixed date of March 11, 2007.
Resolution
For the daylight savings time changeover to occur, a new fixed date must be calculated each calendar year before the Spring changeover date. The changeover date calculation is made following a pre-determined trigger event. The fixed changeover dates used for comparison in the "Formula Date" Daylight Savings option currently get recalculated when:
- The controller’s EEPROM is cleared,
- The controller is reset,
- Any information in the INSTALLATION DATA is modified.
If the "Formula Date" option is selected in a controller, the only means to insure that a controller will process the daylight savings changeover is to either reset the controller or modify the installation data. If it is unknown that either of these events has occurred during the calendar year it will be necessary to manually initiate one of these events to guarantee that the daylight savings time changeover will occur. Refer to Bulletin 01-40
