It has always been my belief that DAY 2 began when the owner started making ANY changes that were not as purchased from the dealer. Since I am deeply entrenched in this day 2 stuff thats my belief in making cars a little better then what you had to purchase from your dealer. This began for some of us on the left coast ripping off all the smog equipment and anything that would slow it down
A day 2 mod might have been performed a few years into ownership when ORIGINAL equipment was changed out.