N: "Really? It hasn't been that long since we started seeing eachother..."
D: "Yeah, it has, its been about three months... you forgot when we first fucked?"
N: "Shit, I forgot our fuck anniversary... our fuckiversary. Tomorrow, Fuckiversary begins."
D: "Ok, were the ... 21st of each month."
A fuckaverssary is a year when you and bae fucked for the first time and you didn't date so this is the date that marks the start of your relationship.
You: Happy fuckaverssary Fabi!
him: Uhh... i guess there's gonna be some tension for the coming days