This is actually a Windows setting, not a DocShuttle or Word setting. Sometimes Windows will display a single-digit month with two digits (like "04" for April), and sometimes it will display it with just one (like "4" for April). Days may be handled similarly.
To change the number of digits in a date, please go to the Windows Control Panel (click Start, then select Control Panel). Then click on the "Regional Settings" icon. There, try changing the format to "mm/dd/yyyy". This will cause single-digit month's to be displayed with two digits always.