I havn't been to Chuckey Cheese in days. (Used to represent several years)
Girl: Hey, wanna come over tonight?
Guy: Is your brother gonna be home?
Girl: Yeah, can you make it?
Guy: Yo look at that girl she's so hot!
Guy #2: DAY! Her hair looks like a mop!
Also, an adverb used to modify an adjective such as long or many.
Dude, she was days cute.
Do you want to go to the lake Saturday?
No man, I can't. I've got days worth of studying to do.
She looks days skanky wearing all that makeup.