Green’s Dictionary of Slang

(US black) the evening, the night.

1942		D. Burley N.Y. Amsterdam Star-News 7 Feb. 16: The other dim, Joe Q. Hipp and Sam D. Home were gunning the stroll.
1944		D. Burley Orig. Hbk of Harlem Jive 64: I was in the mood to jump since I’d been blowin’ the joy roots all the solid dim.
1956		H. Ellison ‘Johnny Slice’s Stoolie’ in Deadly Streets (1983) 86: Even in the dim without much of a moon, I could see the shine of blood.