SetTimeZoneInformation function (timezoneapi.h)

Sets the current time zone settings. These settings control translations from Coordinated Universal Time (UTC) to local time.

To support boundaries for daylight saving time that change from year to year, use the SetDynamicTimeZoneInformation function.

BOOL SetTimeZoneInformation(
  [in] const TIME_ZONE_INFORMATION *lpTimeZoneInformation
);

[in] lpTimeZoneInformation

A pointer to a TIME_ZONE_INFORMATION structure that contains the new settings.

If the function succeeds, the return value is nonzero.

If the function fails, the return value is zero. To get extended error information, call GetLastError.

An application must have the SE_TIME_ZONE_NAME privilege for this function to succeed. This privilege is disabled by default. Use the AdjustTokenPrivileges function to enable the privilege before calling SetTimeZoneInformation, and then to disable the privilege after the SetTimeZoneInformation call. For more information, see Running with Special Privileges.

Windows Server 2003 and Windows XP/2000:  The application must have the SE_SYSTEMTIME_NAME privilege.

To inform Explorer that the time zone has changed, send the WM_SETTINGCHANGE message.

All translations between UTC and local time are based on the following formula:

UTC = local time + bias

The bias is the difference, in minutes, between UTC and local time.

The following example displays the current time zone, then adjusts the time zone one zone west. The old and new time zone names are displayed. You can also verify the changes using Date and Time in Control Panel. The new name is displayed on the Date&Time tab as the Current Time Zone. The new time zone is displayed in the drop-down list on the Time Zone tab. To undo these changes, simply choose your old time zone from the drop-down list.

#define UNICODE 1
#define _UNICODE 1

#include <windows.h>
#include <stdio.h>
#include <string.h>
#include <strsafe.h>

int main()
{
   TIME_ZONE_INFORMATION tziOld, tziNew, tziTest;
   DWORD dwRet;

   // Enable the required privilege

   HANDLE hToken;
   TOKEN_PRIVILEGES tkp;

   OpenProcessToken(GetCurrentProcess(), TOKEN_ADJUST_PRIVILEGES|TOKEN_QUERY, &hToken);
   LookupPrivilegeValue(NULL, SE_TIME_ZONE_NAME, &tkp.Privileges[0].Luid);
   tkp.PrivilegeCount = 1;
   tkp.Privileges[0].Attributes = SE_PRIVILEGE_ENABLED;
   AdjustTokenPrivileges(hToken, FALSE, &tkp, 0, (PTOKEN_PRIVILEGES)NULL, 0);

   // Retrieve the current time zone information

   dwRet = GetTimeZoneInformation(&tziOld);

   if(dwRet == TIME_ZONE_ID_STANDARD || dwRet == TIME_ZONE_ID_UNKNOWN)    
      wprintf(L"%s\n", tziOld.StandardName);
   else if( dwRet == TIME_ZONE_ID_DAYLIGHT )
      wprintf(L"%s\n", tziOld.DaylightName);
   else
   {
      printf("GTZI failed (%d)\n", GetLastError());
      return 0;
   }

   // Adjust the time zone information

   ZeroMemory(&tziNew, sizeof(tziNew));
   tziNew.Bias = tziOld.Bias + 60;
   StringCchCopy(tziNew.StandardName, 32, L"Test Standard Zone");
   tziNew.StandardDate.wMonth = 10;
   tziNew.StandardDate.wDayOfWeek = 0;
   tziNew.StandardDate.wDay = 5;
   tziNew.StandardDate.wHour = 2;

   StringCchCopy(tziNew.DaylightName, 32, L"Test Daylight Zone");
   tziNew.DaylightDate.wMonth = 4;
   tziNew.DaylightDate.wDayOfWeek = 0;
   tziNew.DaylightDate.wDay = 1;
   tziNew.DaylightDate.wHour = 2;
   tziNew.DaylightBias = -60;

   if( !SetTimeZoneInformation( &tziNew ) ) 
   {
      printf("STZI failed (%d)\n", GetLastError());
      return 0;
   }

   // Retrieve and display the newly set time zone information

   dwRet = GetTimeZoneInformation(&tziTest);

   if(dwRet == TIME_ZONE_ID_STANDARD || dwRet == TIME_ZONE_ID_UNKNOWN)    
      wprintf(L"%s\n", tziTest.StandardName);
   else if( dwRet == TIME_ZONE_ID_DAYLIGHT )
      wprintf(L"%s\n", tziTest.DaylightName);
   else printf("GTZI failed (%d)\n", GetLastError());

   // Disable the privilege

   tkp.Privileges[0].Attributes = 0; 
   AdjustTokenPrivileges(hToken, FALSE, &tkp, 0, (PTOKEN_PRIVILEGES) NULL, 0); 

   return 1;
}

GetTimeZoneInformation

SetDynamicTimeZoneInformation

TIME_ZONE_INFORMATION

Time Functions