http://www.merlyn.demon.co.uk/TZ-in-NT.txt



   The following text is from E-mails dated 2002-10-23, 2002-10-27,
      and is reproduced with the permission of the author.  JRS.


        Summer Time and Time Zone Settings in Windows NT

             (c) Chris Freestone, John Stockton 2002.
             ----------------------------------------



There appear to be a couple of MS Knowledgebase articles to do with this
issue, seems that the GMT changeover is far from being the only bug in NT/9x
where timezones and daylight savings are concerned.

Just to note that tzedit is not available on the NT CD, this comes as part
of the NT Resource Kit.  Also there's another, command line based,
application called timezone.exe which was supposed to have been included in
the NT ResKit but wasn't.

See http://support.microsoft.com/default.aspx?scid=kb;en-us;Q194364

This application gives the following arguments:

Daylight Saving Time Update Utility Version 1.00.
Copyright Microsoft Corporation 1997, 1998.  All rights reserved.

TIMEZONE StartDate EndDate

  StartDate     Date that Daylight Saving Time begins (Hour-Day-Month).
  EndDate       Date that Daylight Saving Time ends (Hour-Day-Month).

Example:

  TIMEZONE 02-05-04 22-08-10
  Daylight savings time begins at 2:00 on Apr 5th, 02-05-04, and
  daylight Saving time ends at 22:00 on Oct 8th, 22-08-10.

So this could be used in a login script to correct the information globally.

Tzedit is a GUI based application and shows the list of timezones with the
option to edit short and long names, normal offset from GMT, auto/manual
adjustment for DST, days (format is 1st, 2nd, 3rd, 4th, last - day of week -
month) and times to switch and the number of hours to offset for DST.

Running this on Win 2k shows that GMT for UK is set to roll back at 02:00
DST on the 27th.  On NT it shows 03:00 DST as the roll back time.

All of this information is stored in the Windows registry, location:

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Time Zones

But this is not easily edited in regedit as the timezone information is
stored in a binary format and is hard to decode.

REGEDIT4

[HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Time
Zones\GMT]
"Display"="(GMT) Greenwich Mean Time : Dublin, Edinburgh, Lisbon, London"
"Dlt"="GMT Daylight Time"
"Std"="GMT Standard Time"
"MapID"="0,1"
"TZI"=hex:00,00,00,00,00,00,00,00,c4,ff,ff,ff,00,00,0a,00,00,00,05,00,02,00,\
          00,00,00,00,00,00,00,00,03,00,00,00,05,00,01,00,00,00,00,00,00,00

As NT has "GMT Standard Time" as the registry key for the
Casablanca/Monrovia GMT entry.  The hex is the same and will correct NT's
time zone information.  

A simple registry file could be exported from NT's regedit for the GMT key,
after tzedit had been used to correct the DST information.  This could then
be imported to all machines on a domain in a couple of ways.



Chris Freestone
CEMG IT Systems
Charter Court, Slough

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