Option Explicit
Sub Test()
With CreateObject("Scripting.Dictionary")
.Add "A", "12/07/2017"
.Add "B", "13/07/2017"
.Add "C", CDbl(DateSerial(2017, 7, 12))
ActiveSheet.[A1:A3].Value = WorksheetFunction.Transpose(.Keys)
ActiveSheet.[B1:B3].NumberFormat = "general"
ActiveSheet.[B1:B3].Value = WorksheetFunction.Transpose(.Items)
ActiveSheet.[C1:C3].FormulaR1C1 = "=DAY(RC[-1])&""/""&MONTH(RC[-1])"
MsgBox "Avant application d'un format date.", vbInformation, "Test"
ActiveSheet.[B1:B3].NumberFormat = "m/d/yyyy"
End With
End Sub