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
Holy Week "Great and Holy Week", or "Passion Week". Since the Orthodox liturgical day starts at sunset (as it has from antiquity), Holy Monday services begin Sunday evening, at the normal timing for Monday Vespers (Vespers is the first service of the day). However, during Holy Week, in most parishes, many service times are advanced from six to twelve hours in time and celebrated in anticipation, which permits more of the faithful to attend the most prominent services. Thus, it is the matins service of Great Monday that is on "Palm Sunday" evening in parish churches and often vespers is in the