Is there a Glitch with this Code?

I have 2 identical codes as below, except for what is highlighted below.


Sub callUnDoUpdates()
Dim ws As Worksheet
Application.ScreenUpdating = False
For Each ws In Application.Worksheets
ws.Select
With Range("E2")
..Value = Range("E2").Value - 7 '<====== Other code has an ADD instead of
a Subtract ".Value = Range("E2").Value + 7"
Application.ScreenUpdating = False
End With
Next
Sheet4.Select
Application.ScreenUpdating = True
Application.DisplayAlerts = True
End Sub


It works when the macro is run sometimes(subtracting 7days from the E2
date),
yet other times it jumps from 31 October 2006 to 11 July 2006.

Regards

Corey