How do I find the install time and date of Windows?

Question

This might sound like a little bit of a crazy question, but how can I find out (hopefully via an API/registry key) the install time and date of Windows?

The best I can come up with so far is to look at various files in C:\Windows and try to guess... but that's not exactly a nice solution.

Answer 1

HKLM\SOFTWARE\MICROSOFT\WINDOWS NT\CURRENTVERSION\InstallDate

It's given as the number of seconds since January 1, 1970.

Answer 2

Another question elligeable for a 'code-challenge': here are some source code executables to answer the problem, but they are not complete.
Will you find a vb script that anyone can execute on his/her computer, with the expected result ?

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systeminfo|find /i "install"

would give you the actual date... not the number of seconds ;)

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In Windows PowerShell script, you could just type:

PS > $os = get-wmiobject win32_operatingsystem
PS > $os.ConvertToDateTime($os.InstallDate) -f "MM/dd/yyyy"

By using WMI (Windows Management Instrumentation)

If you do not use WMI, you must read then convert the registry value:

PS > $path = 'HKLM:\SOFTWARE\Microsoft\Windows NT\CurrentVersion'
PS > $id = get-itemproperty -path $path -name InstallDate
PS > $d = get-date -year 1970 -month 1 -day 1 -hour 0 -minute 0 -second 0
## add to hours (GMT offset)
## to get the timezone offset programatically:
## get-date -f zz
PS > ($d.AddSeconds($id.InstallDate)).ToLocalTime().AddHours((get-date -f zz)) -f "MM/dd/yyyy"

The rest of this post gives you other ways to access that same information. Pick your poison ;)

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In VB.Net that would give something like:

Dim dtmInstallDate As DateTime
Dim oSearcher As New ManagementObjectSearcher("SELECT * FROM Win32_OperatingSystem")
For Each oMgmtObj As ManagementObject In oSearcher.Get
    dtmInstallDate =
        ManagementDateTimeConverter.ToDateTime(CStr(oMgmtO bj("InstallDate")))
Next

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In Autoit (a Windows scripting language), that would be:

;Windows Install Date
;
$readreg = RegRead("HKLM\SOFTWARE\MICROSOFT\WINDOWS NT\CURRENTVERSION\", "InstallDate")
$sNewDate = _DateAdd( 's',$readreg, "1970/01/01 00:00:00")
MsgBox( 4096, "", "Date: " & $sNewDate )
Exit

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In Delphy 7, that would go as:

Function GetInstallDate: String;
Var
  di: longint;
  buf: Array [ 0..3 ] Of byte;
Begin
  Result := 'Unknown';
  With TRegistry.Create Do
  Begin
    RootKey := HKEY_LOCAL_MACHINE;
    LazyWrite := True;
    OpenKey ( '\SOFTWARE\Microsoft\Windows NT\CurrentVersion', False );
    di := readbinarydata ( 'InstallDate', buf, sizeof ( buf ) );
//    Result := DateTimeToStr ( FileDateToDateTime ( buf [ 0 ] + buf [ 1 ] * 256 + buf [ 2 ] * 65535 + buf [ 3 ] * 16777216 ) );
showMessage(inttostr(di));
    Free;
  End;
End;