Day 2 - Each day brings with it condfidence as a currency. By day 7 the difference is noticeable, I have to avoid cashing it in this weekend.
I just messed up my 22 day spree. I have no intention of letting that be the end of it! So it's day 0!
Only you can say, it depends on your goals. But keep in mind that it might be harder to quit porn if you keep masturbating, because the fantasies on your mind will have a similar effect and also make your urges stronger. I'd hold that semen if I were you!