DOCUMENT:Q221542 25-APR-2001 [vbwin] TITLE :HOWTO: Change Time Zone Information Using Visual Basic PRODUCT :Microsoft Visual Basic for Windows PROD/VER::5.0,6.0 OPER/SYS: KEYWORDS:kbAPI kbSDKWin32 kbVBp kbVBp500 kbVBp600 kbGrpDSVB ====================================================================== ------------------------------------------------------------------------------- The information in this article applies to: - Microsoft Visual Basic Learning Edition for Windows, versions 5.0, 6.0 - Microsoft Visual Basic Professional Edition for Windows, versions 5.0, 6.0 - Microsoft Visual Basic Enterprise Edition for Windows, versions 5.0, 6.0 ------------------------------------------------------------------------------- SUMMARY ======= It is sometimes necessary to programmatically change the time zone for the system where the application is running. This article demonstrates this technique. 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: HKLM\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Time Zones For Windows 9x, it is located at: HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\Time Zones 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: Pacific Standard Time while in Windows 9x, you would see this key: Pacific The registry location where the current Date/Time settings can be found is: HKLM\SYSTEM\CurrentControlSet\Control\TimeZoneInformation 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 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 lRetVal = SetTimeZoneInformation(TZ) 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 double-click on it. Your system locale is changed to the selected zone. A message box containing the following message is displayed: Time Zone Changed, Click OK to restore 6. Open the control panel and double-click the Date/Time icon. You can also reach this dialog by double-clicking on the clock in the system tray. Click on 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. Additional query words: ====================================================================== Keywords : kbAPI kbSDKWin32 kbVBp kbVBp500 kbVBp600 kbGrpDSVB Technology : kbVBSearch kbAudDeveloper kbZNotKeyword6 kbZNotKeyword2 kbVB500Search kbVB600Search kbVBA500 kbVBA600 kbVB500 kbVB600 Version : :5.0,6.0 Issue type : kbhowto ============================================================================= THE INFORMATION PROVIDED IN THE MICROSOFT KNOWLEDGE BASE IS PROVIDED "AS IS" WITHOUT WARRANTY OF ANY KIND. MICROSOFT DISCLAIMS ALL WARRANTIES, EITHER EXPRESS OR IMPLIED, INCLUDING THE WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. IN NO EVENT SHALL MICROSOFT CORPORATION OR ITS SUPPLIERS BE LIABLE FOR ANY DAMAGES WHATSOEVER INCLUDING DIRECT, INDIRECT, INCIDENTAL, CONSEQUENTIAL, LOSS OF BUSINESS PROFITS OR SPECIAL DAMAGES, EVEN IF MICROSOFT CORPORATION OR ITS SUPPLIERS HAVE BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGES. 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