Every case has a statute of limitations – the date by which it must be filed, or the chances are lost forever. In discrimination cases, sexual harassment, pregnancy discrimination, retaliation, any kind of employment law case, a charge of discrimination must be filed with the United States Equal Employment Opportunity Commission before you’re allowed to file in court, and that charge of discrimination must be filed, within either 180 days of the last discriminatory act or 300 days of the last discriminatory act, depending on the state where you work. So for instance, in New York, that federal filing date with EEOC is 300 days from, if you were fired, that is likely the last discriminatory act. So you must make that deadline of roughly 10 months after the firing to file with the EEOC or you lose your right to sue your employer later on in federal court.
There are other state and local laws that may apply that have different, often longer, statutes of limitations, such as the New York State and the New York City human rights laws that apply discrimination prohibitions to employees who work in New York, and that statute of limitation is three years from the last discriminatory act – much longer. So if you missed the federal deadline, you have considerably more time to threaten or to actually sue your former employer for discrimination under the state and the city anti-discrimination statute.