On April 16th the Orthodox Church marks Maundy Thursday, also known as Holy Thursday, Covenant Thursday, Great and Holy Thursday, and Thursday of Mysteries.

Maundy Thursday 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 day is preceded by Holy Wednesday and followed by Good Friday.

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.

In the Eastern Orthodox Church, the Lenten character of the services is for the most part set aside, and they follow a format closer to normal. The liturgical colors are changed from the somber Lenten hues to more festive colors (red is common in the Slavic practice). The ceremony of the Washing of Feet will normally be performed in monasteries and cathedrals. Because of the joy of the Institution of the Eucharist, on this day alone during Holy Week wine and oil are permitted at meals. In the evening, after the Liturgy, all of the hangings and vestments are changed to black or some other Lenten color, to signify the beginning of the Passion.

In Bulgaria Maundy Thursday is called Veliki Chetvurtuk (Great Thursday), and is traditionally the day when people color their Easter eggs and perform other household chores geared toward preparing for Razpeti Petuk (Crucifixion Friday), Velika Subota (Great Saturday) and Velikden (Easter Day).

Easter eggs can also be colored on Great Saturday. According to the tradition, the first egg is always red and replaces the one from the previous year. The second egg is colored red as well and it is left in the church Saturday evening during the mass, which begins at midnight. The remaining eggs can be of any color.