Maundy Thursday, also known as Holy Thursday, Great and Holy Thursday, and Thursday of Mysteries, is the Christian feast or holy day falling on the Thursday before Easter that commemorates the Last Supper of Jesus Christ with the Apostles. The Mass of the Lord's Supper initiates the Easter Triduum, the three days of Friday, Saturday and Sunday that commemorate the Passion, Death and Resurrection of Jesus. It is normally celebrated in the evening, when according to Jewish tradition Friday begins.
Maundy Thursday is the fifth day of Holy Week, and is preceded by Holy Wednesday and followed by Good Friday. The date is always between 19 March and 22 April inclusive. These dates in the Julian calendar, on which Eastern churches in general base their calculations of the date of Easter, correspond throughout the twenty-first century to 1 April and 5 May in the more commonly used Gregorian calendar. (From: Wikipedia, Licencse: CCA-SA)