"Noone can make you feel inferior without your concent." Eleanor Roosevelt
Many people feel that the 'discovery day (Dday) is the antiversary. The day you found out - or confronted - or whatever.
For me, it is the day he was with the prostitute. I don't even remember the day I found her picture on his computer - I just remember March 9 every year. On that date, I was home with the kids, and he was away - supposedly working - and in a motel room with a whore, getting oral sex.
That is my antiversary.
I think it might be whatever has had the greatest impact on you.
I will not be vanquished. Rose Kennedy