In addition to Brian Seekford's message, here is sample code for using Property Bag in your case:

Private Sub UserControl_ReadProperties(PropBag As PropertyBag)

  nDateFormat = PropBag.ReadProperty("DateFormat", YMD_Format) 'YMD_Format is assigned to nDateFormat if reading is not successful
End Sub

Private Sub UserControl_WriteProperties(PropBag As PropertyBag)

  Call PropBag.WriteProperty("DateFormat", nDateFormat, YMD_Format) 'YMD_Format is written if nDateFormat is empty
EndSub

In addition, move call to InitDateFormat into UserControl_InitProperties event.