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 calendar, while Christian Europe adopted the Julian calendar, in either the Catholic or Orthodox variant. Starting in the 16th century, European settlements in the Americas and elsewhere likewise inherited the Julian calendar of the mother country, until they adopted the Gregorian reform. The last country to adopt the Julian calendar was the Ottoman Empire, which used it for financial purposes for some time under the name Rumi calendar and dropped the "escape years" which tied it to Muslim chronology in 1840. Although the new calendar was much simpler than the pre-Julian calendar, the pontifices initially added a leap day every