Write Filters and Automatic Adjustment of Daylight Saving Time

  • Article

3/21/2011

Automatic Adjustment of daylight saving time (DST) is incompatible with the File-Based Write Filter (FBWF) and the Enhanced Write Filter with HORM (EWF). If Automatic Daylight Saving is enabled while FBWF or EWF is enabled, the system clock will either fall back or spring forward every time the computer is restarted.

The recommended approach to solving issues with DST when using write filters is to change the CMOS clock to use UTC. For more information, see Computer Time Management and Embedded Systems.

Change the CMOS clock to use UTC

  1. Make sure that EWF and FBWF are disabled

  2. Configure the Windows systems Time Zone to the desired value (for example, Pacific Time Zone).

  3. Add the RealTimeIsUniversal key DWORD value to the registry at HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\TimeZoneInformation\.

  4. Change the value of the RealTimeIsUniversal key to 1.

  5. Restart the system and go into the BIOS

  6. Set the CMOS clock to the current UTC time and date. For example, if you are in Pacific Standard Time Zone, and it is 11:00 AM, then you would set the CMOS clock to 7:00 PM as there is 8 hours difference.

  7. Restart the system and enable EWF or FBWF.

See Also

Other Resources

Enhanced Write Filter with HORM
File-Based Write Filter (FBWF)