Based off Conan Gray's "Heather" song. The 3rd of December is supposedly when someone you liked/like gave/gives you a sweater. (from the lyrics: I still remember, 3rd of December, me in your sweater, you said it looked better than me than it did you, only if you knew, how much I liked you.)
"It's the 3rd of December, you're worthy of my sweater."
"Your sweater?"
"I'm saying I like you."
"Yo wtf is that an Evangelion reference??"