How to change time zone information by using Visual Basic (221542)

MORE INFORMATION

The way to implement this effect is as follows:

1. Determine which time zone you would like to change to.
2. Find the key in the registry that contains the information needed to fill the TIME_ZONE_INFORMATION structure.
3. Read in that information and load the values into a variable of type TIME_ZONE_INFORMATION.
4. Call the SetTimeZoneInformation API, passing it the TIME_ZONE_INFORMATION struct variable.

The location in the registry that contains time zone information differs between Windows 9x and Windows NT/Windows 2000.

For Windows NT and Windows 2000, it is located at: For Windows 9x, it is located at: The Time Zone key names differ between Windows NT, Windows 2000, and Windows 9x as well because Windows NT and Windows 2000 append the string "Standard Time" to the different keys whereas Windows 9x does not.

For example:

In Windows NT and Windows 2000, you would see this key:
while in Windows 9x, you would see this key: The registry location where the current Date/Time settings can be found is:

Step-by-step example

The code sample below requires a form with a listbox. The listbox is loaded with the possible time zone values that the user can select with a double-click to change the time zone. It will show a messagebox that, once dismissed, will change the system settings back to their original values.

1. Create a new Standard EXE project. Form1 is created by default.
2. Add a Listbox control to Form1.
3. Add the following code to the General Declarations section of Form1:

   Option Explicit
   
   ' Operating System version information declares
   
   Private Const VER_PLATFORM_WIN32_NT = 2
   Private Const VER_PLATFORM_WIN32_WINDOWS = 1
   
   Private Type OSVERSIONINFO
           dwOSVersionInfoSize As Long
           dwMajorVersion As Long
           dwMinorVersion As Long
           dwBuildNumber As Long
           dwPlatformId As Long
           szCSDVersion As String * 128 ' Maintenance string
   End Type
   
   Private Declare Function GetVersionEx Lib "kernel32" _
   Alias "GetVersionExA" (lpVersionInformation As OSVERSIONINFO) As Long
   
   ' Time Zone information declares
   
   Private Type SYSTEMTIME
      wYear As Integer
      wMonth As Integer
      wDayOfWeek As Integer
      wDay As Integer
      wHour As Integer
      wMinute As Integer
      wSecond As Integer
      wMilliseconds As Integer
   End Type
   
   Private Type REGTIMEZONEINFORMATION
      Bias As Long
      StandardBias As Long
      DaylightBias As Long
      StandardDate As SYSTEMTIME
      DaylightDate As SYSTEMTIME
   End Type
   
   Private Type TIME_ZONE_INFORMATION
      Bias As Long
      StandardName(0 To 63) As Byte ' used to accommodate Unicode strings
      StandardDate As SYSTEMTIME
      StandardBias As Long
      DaylightName(0 To 63) As Byte ' used to accommodate Unicode strings
      DaylightDate As SYSTEMTIME
      DaylightBias As Long
   End Type
   
   Private Const TIME_ZONE_ID_INVALID = &HFFFFFFFF
   Private Const TIME_ZONE_ID_UNKNOWN = 0
   Private Const TIME_ZONE_ID_STANDARD = 1
   Private Const TIME_ZONE_ID_DAYLIGHT = 2
   
   Private Declare Function GetTimeZoneInformation Lib "kernel32" _
   (lpTimeZoneInformation As TIME_ZONE_INFORMATION) As Long
   
   Private Declare Function SetTimeZoneInformation Lib "kernel32" _
   (lpTimeZoneInformation As TIME_ZONE_INFORMATION) As Long
   
   ' Registry information declares
   Private Const REG_SZ As Long = 1
   Private Const REG_BINARY = 3
   Private Const REG_DWORD As Long = 4
   
   Private Const HKEY_CLASSES_ROOT = &H80000000
   Private Const HKEY_CURRENT_USER = &H80000001
   Private Const HKEY_LOCAL_MACHINE = &H80000002
   Private Const HKEY_USERS = &H80000003
   
   Private Const ERROR_SUCCESS = 0
   Private Const ERROR_BADDB = 1
   Private Const ERROR_BADKEY = 2
   Private Const ERROR_CANTOPEN = 3
   Private Const ERROR_CANTREAD = 4
   Private Const ERROR_CANTWRITE = 5
   Private Const ERROR_OUTOFMEMORY = 6
   Private Const ERROR_ARENA_TRASHED = 7
   Private Const ERROR_ACCESS_DENIED = 8
   Private Const ERROR_INVALID_PARAMETERS = 87
   Private Const ERROR_NO_MORE_ITEMS = 259
   
   Private Const KEY_ALL_ACCESS = &H3F
   
   Private Const REG_OPTION_NON_VOLATILE = 0
   
   Private Declare Function RegOpenKeyEx Lib "advapi32.dll" _
      Alias "RegOpenKeyExA" ( _
      ByVal hKey As Long, _
      ByVal lpSubKey As String, _
      ByVal ulOptions As Long, _
      ByVal samDesired As Long, _
      phkResult As Long) _
   As Long
   
   Private Declare Function RegQueryValueEx Lib "advapi32.dll" _
      Alias "RegQueryValueExA" ( _
      ByVal hKey As Long, _
      ByVal lpszValueName As String, _
      ByVal lpdwReserved As Long, _
      lpdwType As Long, _
      lpData As Any, _
      lpcbData As Long) _
   As Long
   
   Private Declare Function RegQueryValueExString Lib "advapi32.dll" _
      Alias "RegQueryValueExA" ( _
      ByVal hKey As Long, _
      ByVal lpValueName As String, _
      ByVal lpReserved As Long, _
      lpType As Long, _
      ByVal lpData As String, _
      lpcbData As Long) _
   As Long
   
   Private Declare Function RegEnumKey Lib "advapi32.dll" _
      Alias "RegEnumKeyA" ( _
      ByVal hKey As Long, _
      ByVal dwIndex As Long, _
      ByVal lpName As String, _
      ByVal cbName As Long) _
   As Long
   
   Private Declare Function RegCloseKey Lib "advapi32.dll" ( _
      ByVal hKey As Long) _
   As Long
   
   ' Registry Constants
   Const SKEY_NT = "SOFTWARE\Microsoft\Windows NT\CurrentVersion\Time Zones"
   Const SKEY_9X = "SOFTWARE\Microsoft\Windows\CurrentVersion\Time Zones"
   
   ' The following declaration is different from the one in the API viewer.
   ' To disable implicit ANSI<->Unicode conversion, it changes the 
   ' variable types of lpMultiByteStr and lpWideCharStr to Any.
   '
   Private Declare Function MultiByteToWideChar Lib "kernel32" ( _
       ByVal CodePage As Long, _
       ByVal dwFlags As Long, _
       lpMultiByteStr As Any, _
       ByVal cchMultiByte As Long, _
       lpWideCharStr As Any, _
       ByVal cchWideChar As Long) As Long
       
   ' The above Declare and the following Constants are used to make
   ' this sample compatible with Double Byte Character Systems (DBCS).
   Private Const CP_ACP = 0
   Private Const MB_PRECOMPOSED = &H1
   Private Declare Sub CopyMemory Lib "kernel32" Alias "RtlMoveMemory" ( _ 
   ByRef Destination As Any, _
   ByRef Source As Any, _
   ByVal numbytes As Long)
   Dim SubKey As String
   
   Private Sub Form_Load()
      Dim lRetVal As Long, lResult As Long, lCurIdx As Long
      Dim lDataLen As Long, lValueLen As Long, hKeyResult As Long
      Dim strvalue As String
      Dim osV As OSVERSIONINFO
   
   ' Win9x and WinNT have a slightly different registry structure. Determine
   ' the operating system and set a module variable to the correct subkey.
   
      osV.dwOSVersionInfoSize = Len(osV)
      Call GetVersionEx(osV)
      If osV.dwPlatformId = VER_PLATFORM_WIN32_NT Then
         SubKey = SKEY_NT
      Else
         SubKey = SKEY_9X
      End If
   
      lRetVal = RegOpenKeyEx(HKEY_LOCAL_MACHINE, SubKey, 0, _
                             KEY_ALL_ACCESS, hKeyResult)
   
      If lRetVal = ERROR_SUCCESS Then
   
         lCurIdx = 0
         lDataLen = 32
         lValueLen = 32
   
         Do
            strvalue = String(lValueLen, 0)
            lResult = RegEnumKey(hKeyResult, lCurIdx, strvalue, lDataLen)
   
            If lResult = ERROR_SUCCESS Then
               List1.AddItem Left(strvalue, lValueLen)
            End If
   
            lCurIdx = lCurIdx + 1
   
         Loop While lResult = ERROR_SUCCESS
   
         RegCloseKey hKeyResult
      Else
         List1.AddItem "Could not open registry key"
      End If
   End Sub
   
   Private Sub List1_DblClick()
      Dim TZ As TIME_ZONE_INFORMATION, oldTZ As TIME_ZONE_INFORMATION
      Dim rTZI As REGTIMEZONEINFORMATION
      Dim bytDLTName(32) As Byte, bytSTDName(32) As Byte
      Dim cbStr As Long, dwType As Long
      Dim lRetVal As Long, hKeyResult As Long, lngData As Long
   
      lRetVal = RegOpenKeyEx(HKEY_LOCAL_MACHINE, SubKey & "\" & List1.Text, _
                              0, KEY_ALL_ACCESS, hKeyResult)
   
      If lRetVal = ERROR_SUCCESS Then
         lRetVal = RegQueryValueEx(hKeyResult, "TZI", 0&, ByVal 0&, _
                                     rTZI, Len(rTZI))
   
         If lRetVal = ERROR_SUCCESS Then
            TZ.Bias = rTZI.Bias
            TZ.StandardBias = rTZI.StandardBias
            TZ.DaylightBias = rTZI.DaylightBias
            TZ.StandardDate = rTZI.StandardDate
            TZ.DaylightDate = rTZI.DaylightDate
   
            cbStr = 32
            dwType = REG_SZ
   
            lRetVal = RegQueryValueEx(hKeyResult, "Std", _
                        0&, dwType, bytSTDName(0), cbStr)
   
            If lRetVal = ERROR_SUCCESS Then
               Call MultiByteToWideChar(CP_ACP, MB_PRECOMPOSED, _
                  bytSTDName(0), cbStr, TZ.StandardName(0), 32)
            Else
               RegCloseKey hKeyResult
               Exit Sub
            End If
   
            cbStr = 32
            dwType = REG_SZ
   
            lRetVal = RegQueryValueEx(hKeyResult, "Dlt", _
                        0&, dwType, bytDLTName(0), cbStr)
   
            If lRetVal = ERROR_SUCCESS Then
               Call MultiByteToWideChar(CP_ACP, MB_PRECOMPOSED, _
                  bytDLTName(0), cbStr, TZ.DaylightName(0), 32)
            Else
               RegCloseKey hKeyResult
               Exit Sub
            End If
   
            lRetVal = GetTimeZoneInformation(oldTZ)
   
            If lRetVal = TIME_ZONE_ID_INVALID Then
               MsgBox "Error getting original TimeZone Info"
               RegCloseKey hKeyResult
               Exit Sub
            Else
            If TZ.DaylightDate.wMonth <> 0 And TZ.DaylightBias <> 0 Then
               lRetVal = SetTimeZoneInformation(TZ)
            Else
              Call CopyMemory(TZ.DaylightName(0), TZ.StandardName(0), 64)
              TZ.DaylightBias = 0
              lRetVal = SetTimeZoneInformation(TZ)
            End If
               MsgBox "Time Zone Changed, Click OK to restore"
               lRetVal = SetTimeZoneInformation(oldTZ)
            End If
         End If
   
         RegCloseKey hKeyResult
      End If
   End Sub
   					

4. Run the program, and note that the listbox displays all of the available time zones.
5. Select a time zone, and then double-click it. Your system locale is changed to the selected zone. You receive the following message: Time Zone Changed, Click OK to restore
6. In Control Panel, double-click the Date/Time icon. You can also reach this dialog by double-clicking the clock in the system tray. Click the Time Zone tab and observe that the time zone has been changed.
7. Close the Date/Time Properties dialog box and click OK on the message box displayed by your application. Repeat the previous step to confirm that the time zone information has been restored.