Green’s Dictionary of Slang

(US/UK black) unpunctuality, lateness.

1966		K. Porter ‘Still More Ethnic and Place names as Derisive Adjectives’ Western Folklore XXV:1 38: Colored folks’ time. An hour or two later than the prescribed time [...] Howard University. ca. 1945.
1980		Eble Campus Sl. Spring 2: CP time – colored people’s time, a little late: Everyone be at church at 11 A.M. sharp, not CP time.
1997		C. Newland Scholar 156: The Dredd had ushered them into a room which had hitherto been locked, to wait for Kenny who ran on BPT – black people’s time.