 Liturgical calendars began to be developed in Christianity around the fourth century, with the church calendar as it is known today coming into full development in the period of the medieval sacramentaries.While Sunday had long been established in the weekly calendar, festivals such as Easter and Christmas were also a fixed part of the calendar by this time.The ninth century also saw the inclusion of numerous saints in the calendar (a practice already begun by the second century), even to the point that normal Sunday propers were taking place over those normally appointed for Sunday.