Public Sub dateconvert()
Dim cell As Range, jour As String, mois As String, an As String
For Each cell In Range("M1:M" & Range("M65536").End(xlUp).Row)
If cell > 0 Then
jour = Val(Right(cell, 2))
mois = Val(Mid(cell, 5, 2))
an = Val(Left(cell, 4))
cell = Format(DateSerial(an, mois, jour), "dd-mm-yyyy")
End If
Next
End Sub