Where do Windows 2000 and Windows NT store time zone information?

A. From the Control Panel Date/Time applet, select the Time Zone tab to set the local country and its associated time difference. You can select the same tab to enable daylight saving.

Changing these settings updates the registry values under the HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\TimeZoneInformation key. I’ve listed the most useful time-zone values below.

ActiveTimeBias This value is the current time difference from Greenwich Mean Time (GMT) in minutes and is the difference for GMT. For example, if you’re 1 hour ahead, GMT is 1 hour behind. The value would be ffffffc4, which is hexadecimal for -60.
Bias This value is the normal time difference from GMT, excluding daylight saving in minutes. The value is the difference for GMT, so if you’re 3 hours ahead (e.g., if you live in Moscow), the Bias would be ffffff4c, which is hex for 180. If you’re 2 hours behind GMT (e.g., if you're on a boat in the mid-Atlantic Ocean), GMT is 2 hours ahead, so the value is 120.
DaylightBias This value is the time difference used for daylight saving for GMT. If you're 1 hour ahead, the value is ffffffc4, which is hex for -60. Notice that the ActiveTimeBias is the sum of Bias and DaylightBias in daylight saving months, which is the same as Bias for standard months.
DaylightName The OS uses this name during daylight saving months.
StandardName The OS uses this name during non-daylight saving months.
DaylightStart This value tells the computer when to start daylight mode.
StandardStart This value tells the computer when to start standard mode.
DisableAutoDaylightTimeSet This value exists only if you clear the checkbox for the option Automatically adjust clock for daylight saving and if you set the value to 1.

Using the Microsoft Windows 2000 Resource Kit or the Microsoft Windows NT Resource Kit reg.exe utility, you can use the following command to query these values from the command line:

C:\&gt;reg query hklm\system\currentcontrolset\control\timezoneinformation\bias<br>
REG_DWORD       bias    0<br><br>
C:\&gt;reg query hklm\system\currentcontrolset\control\timezoneinformation\daylightname<br>
REG_SZ          daylightname    GMT Daylight Time
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