I just interpreted this using my logic: "Sober" date is technically incompatible with a day when I'm still drinking, so the day after.
I had an "incident" though a couple weeks into my first quitting though, which is kinda funny in retrospect. I was out with two friends in a restaurant, they ordered cocktails, and I got curious about how one of them tasted, so I took two sips from his glass. I had no conscious desire to drink any more or to order a drink for myself. We then had appetizers. Next thing I know, I'm having a serious allergic reaction, and we are heading to the ER... My crazy mind associated the sip from the cocktail with that reaction ("allergy to alcohol", literally). Of course the doctors told me it's more than unlikely. It did scare me though, and I came to SR right after being back from the ER to report this... Then I was told that it might be helpful to change my sobriety date even though I did not get drunk at all from those two sips, to remind me of my commitment to never drink in any form. So I did. I found out later what caused the allergic reaction, it was a type of fish, and I even got it later again with the same result. It's still a weird and scary memory in my mind though.
I think it's best to use whatever is helpful for an individual.