For most types of civil claims, the clock begins running on the limitations period when the person with the claim knew or should have know they have suffered damages as a result of the defendant's conduct. This is called the 'discovery rule.'
In contract cases, the discovery rule generally does not apply, unless the breach was not possible to ascertain.
The exact timelines vary by the type of case, but here are the most common statutes of limitations:
Discrimination, sexual harassment, or retaliation for reporting discrimination or harassment: 300 days
Claims under the federal FMLA: 2 years
Claims under Massachusetts PFMLA, wage and hour claims, and fraud, misrepresentation, or other tort claims: 3 years
Claims under Massachusetts Chapter 93A (unfair business practices): 4 years
Contract claims: 6 years.