Do you know that you can edit that activity, and change the date? Your almost 2 decades old device likely lost the time/date sync (possibly while discharged?), so if it still shows the wrong date, have a look at the date/time settings. I have no idea how Edge 500 worked, but recent models sync the date and time either from GPS, or from the phone, or from a computer (when connected over the USB cable to Garmin Express).
