Sub Convertir()
Dim d&, tablo, i&
d = [A65536].End(xlUp).Row
tablo = Application.Transpose(Range("A1:A" & d))
On Error Resume Next 'si toutes les valeurs ne sont pas des dates
For i = 1 To d
tablo(i) = CDbl(CDate(tablo(i)))
Next
With [A1].Resize(d)
.NumberFormat = "dd/mm/yyyy" 'ou autre format Date
.Value = Application.Transpose(tablo)
End With
End Sub