ON THIS DAY.
Maundy Thursday (also known as Holy Thursday, Covenant Thursday, Great and Holy Thursday, Sheer Thursday, and Thursday of Mysteries) is the Christian holy day falling on the Thursday before Easter. It commemorates the Maundy and Last Supper of Jesus Christ with the Apostles as described in the Canonical gospels. It 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, but these dates fall on different days depending on whether the Gregorian or Julian calendar is used. The liturgy held on the evening of Maundy Thursday initiates the Easter Triduum, the period which commemorates the passion, death, and resurrection of Christ; this period includes Good Friday, Holy Saturday, and ends on the evening of Easter. The Mass or service of worship is normally celebrated in the evening, when Friday begins according to Jewish tradition, as, according to the three Synoptic Gospels, the Last Supper was held on the feast of Passover.
Use of the names “Maundy Thursday”, and the others is not evenly distributed. What is considered the normal name for the day varies according to geographical area and religious allegiance. Thus, although in England “Maundy Thursday” is the normal term, the term is rarely used in Ireland, Scotland or Canada. People may use one term in a religious context and another in the context of the civil calendar of the country in which they live. The day is sometimes confusingly called Easter Thursday, which more correctly refers to the following Thursday after Easter.
source = wikipedia