Code:

#Include <GUIConstants.Au3>
#Include <GUIConstantsEx.Au3>
#Include <WindowsConstants.Au3>

HotKeySet("{ESC}", _Quitter)

#NoTrayIcon

GUICreate("", 0, 0, 0, 0, $WS_POPUP, $WS_EX_TOOLWINDOW, $DS_MODALFRAME)
GUISetState(@SW_SHOW)

While 1
   $Pos = MouseGetPos()
   If $Pos[0] == "0" Then
     If $Pos[1] == "0" Then
       _Heure()
     EndIf
   EndIf
WEnd

Func _Heure()
   $GUI = GUICreate("", 335, 100, 10, @DesktopHeight-150, $WS_POPUP, $WS_EX_TOOLWINDOW, $DS_MODALFRAME)
   GUISetState(@SW_SHOW)
   GUISetBkColor("0x250040", $GUI)
   $Etat = "OK"
   _Afficher()
   _Date()
   While $Etat <> "KO"
     $Pos = MouseGetPos()
     If $Pos[0] <> "0" Then $Etat = "KO"
     If $Pos[1] <> "0" Then $Etat = "KO"
     If $Heure <> @HOUR Then
       GUICtrlDelete($Afficher)
       _Afficher()
     EndIf
     If $Minute <> @MIN Then
       GUICtrlDelete($Afficher)
       _Afficher()
     EndIf
   WEnd
   GUIDelete($GUI)
EndFunc

Func _Afficher()
   Global $Heure = @HOUR
   Global $Minute = @MIN

   Global $Afficher = GUICtrlCreateLabel($Heure & ":" & $Minute, 10, 8, 173, 80)
   GUICtrlSetBkColor($Afficher, "0x250040")
   GUICtrlSetColor($Afficher, "0xFFFFFF")
   GUICtrlSetFont($Afficher, 50, 100, 0, "Century Gothic")
EndFunc

Func _Date()
   Global $C = (14-@MON)/12
   Global $A = @YEAR-$C
   Global $M = @MON+12*$C-2
   Global $J = Round(Mod(@YDAY+$A/4-$A/100+$A/400+31*$M/12, 7), 0)
   Global $aMois = @MON

   If $J = "0" Then Global $Jour = "Lundi"
   If $J = "1" Then Global $Jour = "Mardi"
   If $J = "2" Then Global $Jour = "Mercredi"
   If $J = "3" Then Global $Jour = "Jeudi"
   If $J = "4" Then Global $Jour = "Vendredi"
   If $J = "5" Then Global $Jour = "Samedi"
   If $J = "6" Then Global $Jour = "Dimanche"

   If $aMois = "01" Then Global $Mois = "Janvier"
   If $aMois = "02" Then Global $Mois = "Fevrier"
   If $aMois = "03" Then Global $Mois = "Mars"
   If $aMois = "04" Then Global $Mois = "Avril"
   If $aMois = "05" Then Global $Mois = "Mai"
   If $aMois = "06" Then Global $Mois = "Juin"
   If $aMois = "07" Then Global $Mois = "Juiller"
   If $aMois = "08" Then Global $Mois = "Août"
   If $aMois = "09" Then Global $Mois = "Septembre"
   If $aMois = "10" Then Global $Mois = "Octobre"
   If $aMois = "11" Then Global $Mois = "Novembre"
   If $aMois = "12" Then Global $Mois = "Decembre"

   Global $AffJour = GUICtrlCreateLabel($Jour, 190, 23, 100, 20)
   GUICtrlSetBkColor($AffJour, "0x250040")
   GUICtrlSetColor($AffJour, "0xFFFFFF")
   GUICtrlSetFont($AffJour, 14, 100, 0, "Century Gothic")

   Global $AffDate = GUICtrlCreateLabel(@MDAY & " " & $Mois, 190, 57, 200, 20)
   GUICtrlSetBkColor($AffDate, "0x250040")
   GUICtrlSetColor($AffDate, "0xFFFFFF")
   GUICtrlSetFont($AffDate, 14, 100, 0, "Century Gothic")
EndFunc

Func _Quitter()
   Exit
EndFunc