Sub ConvertirDates()
Dim col%, a, t, i&, x$, j As Byte
col = 2 'conversion de la colonne B, à adapter
a = Array("January", "February", "March", "April", "May", "June", "July", "August", "September", "October", "November", "December")
With Columns(col).Resize(Cells(Rows.Count, col).End(xlUp).Row + 1) 'au moins 2 éléments
t = .Value 'matrice, plus rapide
For i = 1 To UBound(t) - 1
x = CStr(t(i, 1))
For j = 1 To 12
If InStr(x, a(j - 1)) Then
x = Replace(x, a(j - 1), "/" & j & "/")
If IsDate(x) Then t(i, 1) = CDate(x)
Exit For
End If
Next j, i
.Value = t
End With
End Sub