Open scan dialog and save output to desktop with dd/mm/yyyy format.

skannaa.vbs

Set objFSO = CreateObject("Scripting.FileSystemObject")

Function LPad(s, l, c)
  Dim n : n = 0
  If l > Len(s) Then n = l - Len(s)
  LPad = String(n, c) & s
End Function

Function FileExists(FilePath)
  Set fso = CreateObject("Scripting.FileSystemObject")
  If fso.FileExists(FilePath) Then
    FileExists=CBool(1)
  Else
    FileExists=CBool(0)
  End If
End Function

targetTime = Now()
'targetTime = CDate("2021-01-01 3:00:00")

If Hour(targetTime) <= 5 Then
    targetTime = DateAdd("d", -1, targetTime)
End If

set oDlg = CreateObject("WIA.CommonDialog")
set image = oDlg.ShowAcquireImage()

set WshShell = WScript.CreateObject("WScript.Shell")
strDesktop = WshShell.SpecialFolders("Desktop")

strFileName = Year(targetTime) & " " & LPad(Month(targetTime), 2, "0") & " " & LPad(Day(targetTime), 2, "0")

strCombinedPath = objFSO.BuildPath(strDesktop, strFileName)

Dim strFinalFilename : strFinalFilename  = strCombinedPath & ".jpg"

If FileExists(strCombinedPath & ".jpg") Then
    Dim i : i = 1
    Do While FileExists(strCombinedPath & " (" & i & ").jpg")
        i=i+1
    Loop
    strFinalFilename = strCombinedPath & " (" & i & ").jpg"
End If

image.SaveFile(strFinalFilename)