Picking an anniversary date

So my bf and I don’t have a set day we got official. But I wanted to pick a date and idk how. This might sound dumb but so technically we became exclusive officially early July so it would make sense to pick a date then. But my ex bf and I got together early July too and I don’t want this relationship to have the same timeline. I want it to have its own. But I can’t tell my bf this.

We started talking in June so i was thinking of choosing a day in June if my bf is good with that. But the only issue is probably a couple weeks before we got exclusive I did kiss another man. We weren’t exclusive so i didn’t do anything wrong. It was a drunken kiss with a guy I knew, haven’t talked to him since that day.

My only problem is if we pick a day in June, it’ll have been before this kiss which is not ok right???

And my bf doesn’t know about the kiss bc I see no reason why he would need to know.

Anyway, what’s your opinion?

I guess I could pick a day in august??? Idk it doesn’t matter in the long run but some point this summer I guess

I want it to be June. But is it bad that then technically after that I had kissed another guy?

Edit: I have no idea which day it was that we chose to be exclusive. He doesn’t know either. That’s why we decided we can pick a date together