Time Stamp Changes with Daylight Savings

• Microsoft Windows NT operating system version 3.1
• Microsoft Windows NT Advanced Server version 3.1
• Microsoft Windows NT Workstation versions 3.5, 3.51, 4.0
• Microsoft Windows NT Server versions 3.5, 3.51, 4.0

SUMMARY

When Windows NT automatically adjusts for daylight savings time, the times on files on Windows NT file system (NTFS) partitions and the events in the event logs are retroactively shifted by one hour, even though the files and event records were created before the daylight savings time change.

NOTE: To configure Windows NT to automatically adjust for daylight savings time, run Control Panel, choose Date/Time, and select "Automatically Adjust for Daylight Saving Time."

MORE INFORMATION

This behavior occurs because of the way that Windows NT stores time information. All times displayed in Windows NT for event log events and files on NTFS partitions are computed as offsets to Greenwich Mean Time (GMT). When you set the time on your system, you are setting the value for GMT. When you select your local time zone for the system, the appropriate number of hours are added or subtracted to the stored GMT value. This adjusted time is displayed. When "Automatically Adjust for Daylight Saving Time" is selected, an additional hour is added to GMT during daylight savings time (the first Sunday in April through the last Sunday in October).

If you are viewing another machine remotely across one or more time zones through Event Viewer, the times for events on the remote system appear relative to your local time. In other words, if you are viewing an event remotely that actually occurred at 8:00 PM Central Daylight Time, the time displayed for the event on your computer will be 6:00 PM when you view the event from the Pacific Daylight Time zone.

When Windows95 or Windows NT clients access network resources they are passed the GMT time of the file stored on the NTFS partition. When the client recieves the time stamp in GMT they then adjust the time stamp (+) plus or (-) minus the time zone they are set for.

In the case of WINDOWS NT - it also adjusts for daylight savings time and displays the file's time stamp for the correct local time including Daylight Savings Time setting.



In the case of WINDOWS95 - The time returned by the file system is not adjusted for Daylight Savings Time. This feature is by design, and was implemented to work with servers such as NetWare that do not support the Daylight Savings time APIs and time functions in Windows 95. In this case the files will display off by one hour. this is BY DESIGN for WINDOWS95 clients.

Additional query words: prodnt day light

Keywords          : kbusage ntconfig ntfilesys 
Version           : 3.1 3.5 3.51
Platform          : winnt 
Issue type        : 

Last Reviewed: February 27, 1999