Thanks for adding, fimpster. I've never tried setting the date back, but I would imagine it's not possible on our machine as well.
I actually read the decision on the NE Supreme Court website (because it's NE, and I'm a geek like that

), and the issue had more to do with the fact that the letter was properly addressed and sent by Certified Mail on Sept. 1, well before the Sept. 12 deadline, but was returned to the mailer on Sept. 15. The mailer then simply ran the same envelope through the meter again to add a Return Receipt. The tax commission received it on Sept. 20.
The decision does address the possibility of manually changing dates, though:
Quote:
The current regulations clearly require mail to be dated accurately. Furthermore, in the absence of a contrary indication, lawful conduct—that mailers comply with the regulations—is presumed. Moreover, though those regulations are missing, it remains true that the USPS authorizes and heavily regulates postage meter use and that misuse of a postage meter can result in significant penalties. Under such circumstances, and in the absence of evidence showing that the mailer misused the meter, we conclude that a postage meter stamp satisfies the statute's purpose of being evidence of the mailing date and that it is a "postmark."
http://www.supremecourt.ne.gov/site.../s12-322.pdf (endnote references removed)