I sent an email today with a spreadsheet attached.In the header I had "Aug.1,2012' typed. In the footer I had 8/1/2012 typed. I sent this email to 4 recipients. On the spreadsheet sent to one of the four the header and footer changed to "June 1,2012" and 6/1/2012"

The other three were received correctly. How can this be?
Thanks