I know this won't help for now, but whenever we go to WDW, on the last day (or so) we go into Guest Services, find out how many days left on Park hoppers, then write it on a piece of masking tape, afixed to the back. This last trip we were bringing 3 partially used PH passes. Seems we've always got partially used ones because DH only goes to the parks 2 or 3 days per trip, so we've learned to do this. Then next trip, we take out the PH, and immediately know how many days there are by looking at the tape.