Mass is celebrated at 5:30 PM on Holy (AKA Spy) Wednesday.
In the New Testament, just after Palm Sunday, the Sanhedrin gathered together and plotted to kill Jesus, even before the feast of Pesach. On the Wednesday before his death Jesus was in Bethany, in the house of Simon the Leper. As they sat at the supper table, a woman named Mary anointed Jesus’ head and feet with costly oil of spikenard. The disciples were indignant, asking why the oil was not instead sold and the money given to the poor. But Judas Iscariot wanted to keep the money for himself. Then Judas went to the Sanhedrin and offered to deliver Jesus to them in exchange for money. From this moment on, Judas sought an opportunity to betray Jesus.
In reference to Judas Iscariot’s intent to betray Jesus, formed on Holy Wednesday, the day is sometimes called “Spy Wednesday.” (The word spy, in obsolete usage, could mean “ambush, ambuscade, snare”.)
More at Wikipedia.
Image: Judas kisses Jesus. Detail from “Judas’ Betrayal” Fresco, St.Clement Church, Ohrid, Macedonia.