Maundy Thursday April 22 inclusive, but these dates fall on different days depending on whether the Gregorian calendar or Julian calendar is used liturgically. Eastern churches generally use the Julian calendar and celebrate this feast throughout the 21st century between April 1 and May 5 in the more commonly used Gregorian calendar. The liturgy held on the evening of Maundy Thursday initiates the Easter Triduum, the period which commemorates the passion, death, and resurrection of Jesus; this period includes Good Friday and Holy Saturday, and ends on the evening of Easter. The Mass of the Lord's Supper or service of worship is
Julian calendar change for civil purposes on 16 February/1 March 1923, but the next national day (25 March)—a religious holiday—took place as if on the old calendar. Most Christian denominations in the west and areas evangelised by western churches have made the same change for their liturgical calendars. A calendar similar to the Julian one, the Alexandrian calendar, is the basis for the Ethiopian calendar, which is still the civil calendar of Ethiopia. Egypt converted from the Alexandrian calendar to Gregorian on 1 Thaut 1592/11 September 1875. During the changeover between calendars and for some time afterwards, dual dating was used in