Endiversary
The date in which two friends or a couple stop talking or have ended their relationship.
“Our Endiversary is on November 20th”
Endiversary
Opposite of an anniversary. It's the day you either celebrate (or mourn, depending on your outlook of the situation) the ending of a relationship. Causes of celebration include the end of a marriage from a cheating whore. Causes of mourning is when the relationship ends abruptly and you didn't want it to.
January 30 is my endiversary from my ex-wife! It's going to be a great day! We'll all go out and get hammered to celebrate!