Sub ChangeDate()
CompteurLigne = Range('a2').End(xlDown).Row
Range('a2:a' & CompteurLigne).Select
On Error Resume Next
For Each c In Selection
If Left(c, 2) > 12 Then
Range('a' & c.Row) = CDate(Left(c, 10))
Else
Range('a' & c.Row) = Left(c, 10)
End If
Next c
End Sub