Sub test()
Dim i&,tablo
tablo = Feuil1.[A2].Resize(ActiveSheet.UsedRange.Rows.Count).Value
For i = 1 To UBound(tablo)
If tablo(i, 1) <> "" Then tablo(i, 1) = DateSerial(Mid(tablo(i, 1), 1, 4), Mid(tablo(i, 1), 5, 2), Mid(tablo(i, 1), 8, 2))
Next
[B2].Resize(UBound(tablo)) = tablo
End Sub