How To Set the System Time (154009)

SUMMARY

The Win32 SetSystemTime API function offers the functionality to change the system time on the local machine. The change will take place immediately without the need for a reboot. This article illustrates how to create a sample project that sets the system time using the SetSystemTime function. The SetSystemTime function sets the system time based on coordinated universal time (UTC). UTC-based time is loosely defined as the current date and time of day in Greenwich, England.

MORE INFORMATION

Start a new project in Visual Basic. Form1 is created by default.

Add the following code to the General Declarations section of Form1:

      Option Explicit

      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 Declare Function SetSystemTime Lib "kernel32" (lpSystemTime _
        As SYSTEMTIME) As Long

      Private Sub Form_Load()
        Dim lReturn As Long
        Dim lpSystemTime As SYSTEMTIME
        lpSystemTime.wYear = 1996
        lpSystemTime.wMonth = 6
        lpSystemTime.wDayOfWeek = 5
        lpSystemTime.wDay = 28
        lpSystemTime.wHour = 9
        lpSystemTime.wMinute = 42
        lpSystemTime.wSecond = 0
        lpSystemTime.wMilliseconds = 0
        lReturn = SetSystemTime(lpSystemTime)
      End Sub

Run the project by pressing the F5 key. Check the system time and date in the Control Panel. The time should have changed to reflect the UTC-based time settings used in the sample.

REFERENCES

The SYSTEMTIME Type structure is as follows:

   WYear           Integer-The current year.
   WMonth          Integer-The current month. January is 1.
   WDayOfWeek      Integer-The current day of the week. Sunday is 0.
   WDay            Integer-The current day of the month.
   WHour           Integer-The current hour.
   wMinute         Integer-The current minute.
   wSecond         Integer-The current second.
   wMilliseconds   Integer-The current millisecond.

To change the system time on a Win32 platform from 16-bit Visual Basic, you would have to create a DLL that does a generic thunk to the 32-bit API SetSystemTime.