I have lots that dont enter a date at all, but as long as were EFiling on that same day I signed/dates, I dont really worry about it, but when its been weeks between my date and their signing, I make sure a date gets entered, I dont want it to look like stock piling.  Weve got 3 days to transmit from the time they sign the 8879.   

When people mail them back to me and the form was signed/dated a week before they finally mailed it, I write on the top of the form the date I received it  in the mail,  just in case IRS ever checks dates.