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JSI Tip 0398 - How to set the time zone by editing the registry.
Jerold Schulman
January 20, 1998
2 Min Read
HKEY_LOCAL_MACHINESYSTEMCurrentControlSetControlTimeZoneInformationValue | Type | Description |
|---|---|---|
Bias | REG_DWORD | Negative offset from GMT in minutes. |
StandardName | REG_SZ | Standard name of this time zone. |
StandardBias | REG_DWORD | Offset applied to Bias for Standard Time. |
StandardStart | REG_BINARY | A coded year, month, day of week, week, hour, minute, second, and millisecond of when the switch to Stand Time occurs. This is detailed at the end of the tip. |
DaylightName | REG_SZ | Standard name for Daylight time. |
DaylightBias | REG_DWORD | Offset applied to StandardBias wich is applied toBias for Daylight Time. |
DaylightStart | REG_BINARY | A coded year, month, day of week, week, hour, minute, second, and millisecond of when the switch to Daylight Time occurs. This is detailed at the end of the tip. |
ActiveTimeBias | REG_WORD | The currently active offset from GMT. |
If your browse to your time zone starting at:
HKEY_LOCAL_MACHINESoftwareMicrosoftWindows NTCurrentVersionTime Zones
you will find Display contains your StandardName, DLT contains your DaylightName, and TZI contains everything else. Here is the TZI for Western Europe Standard Time and its' meaning:
C4 FF FF FF 00 00 00 00 C4 FF FF FF 00 00 0A 00 00 00 05 00 03 00 00 00 00 00 00 00 00 00 03 00 00 00 05 00 02 00 00 00 00 00 00 00
TDI Bytes | Hex Value | Decimal | Meaning |
|---|---|---|---|
C4 FF FF FF | ffffffc4 | -60 | Bias |
00 00 00 00 | 00000000 | 0 | StandardBias |
C4 FF FF FF | ffffffc4 | -60 | DaylightBias |
00 00 0A 00 00 00 05 00 03 00 00 00 00 00 00 00 | Switch to Standard time (last Sun in Oct, 3:00 am) | StandardStart |
Where (looking at StandardStart)
00 00 - is the Year from a 1900 time base.
0A 00 - The first byte is the Month (January is 01).
00 00 - The first byte is the DayOfWeek (Sunday=0).
05 00 - The first byte is the Week (starts at 1 and 5 means last).
03 00 - The first byte is the Hour.
00 00 - The fist byte is the Minute.
00 00 - The first byte is the Seconds.
00 00 - the first byte is the Millisecond.
If no switch to/from DST is required, Month is 0.
If the switch happens on a date specified in absolute terms, Year not = 0, then all the fields are the date when the switchover happens.
If the switch date is variable, Year = 0, then Month is the month for the switch, DayOfWeek is the weekday, and Week selects the Nth occurrence of the specified weekday within the month.
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