Look at the vague question you asked and you complain my answer was too vague?
the continuing violations doctrine rests on the assumption that if alleged discrimination is part of a “continuing pattern of discrimination,” then the plaintiff should be allowed to bring the claim based on the entire pattern of conduct, not just those acts occurring within the filing period. National Railroad Passenger Corp. v. Morgan.
The Supreme Court held that on conduct outside the charge-filing period, so long as at least one event constituting the hostile work environment occurred during the charge-filing period, predicating its distinction between the two situations on its characterization of a hostile work environment claim as “a single unlawful employment practice.”
Hostile environment claims are different in kind from discrete acts. Many circuits, including the Tenth, had limited the reach of the continuing violations doctrine in cases where the plaintiff knew he had a cause of action, but even then delayed filing. The Supreme Court expressly rejected this test in the context of a hostile work environment claim.
“In order for the charge to be timely, the employee need only file a charge within 180 or 300 days of any act that is part of the hostile work environment.” For an act to be part of a hostile work environment the act need only “contribut[e]” to the hostile work environment. Id.
Under Morgan discrete act claims are considered “different in kind” from hostile work environment claims such that the filing period for such claims can be extended only through equitable doctrines such as tolling. But, hostile environment claims can be based upon acts outside of the statute of limitations period.