Holding that a knowing plaintiff has an obligation to file promptly or lose his claim as "distinguished from a plaintiff who is unable to appreciate that he is being discriminated against until he has lived through a series of acts and is thereby able to perceive the overall discriminatory pattern."
Holding that "a plaintiff may raise an inference of intentional, racially-disparate treatment without proving that he technically applied for, and failed to obtain, the promotion" because of an "informal, secretive selection process"