Christian Holidays In Vietnam: How does this affect students? There are no work-restricted holy days within the Christian faith by tenet. By custom, in the United States, Easter and Christmas are considered to be non-work days. Many dates in this calendar are recognizedas denominational, sacred or holy. These dates are observed by persons or groups who are required—through a set or system of religious beliefs, law/doctrines, tenets, canons or theology—to restrict or limit work and/or physical or mental activity directed towards the production or accomplishment of something; toil; labor. This definition may include academic endeavors (e.g. examinations, classroom activities and research, or out-of-classroom learning experiences)..