In the early days of our Church, just as today, there were many different beliefs. The society was very agricultural, and many religions used the seasons to celebrate special feasts. It was important, in teaching about Jesus, to have people connect the Gospel message to their daily lives. Since Jesus' resurrection was the beginning of a whole new life and occurred so near the spring feasts, it was determined that Easter would always be calculated as the first Sunday after the first full moon after the vernal equinox (that is, the first day of spring).
The Sacred Triduum
Sundown on Holy Thursday to sundown on Easter Sunday is considered the most solemn part of the liturgical year. This three-day period is referred to as the Easter Triduum, also known as the Sacred Triduum, or Paschal Triduum.
The Sacred Triduum is one great festival recounting the last three days of Jesus’ life on earth, the events of his Passion and Resurrection, when the Lamb of God laid dow his life in atonement for our sins.
Sunday: Celebrating the Resurrection
The third commandment obliges us to keep holy the Sabbath, which is the seventh day of the week, the day on which God rested after creating the world. The first Christians rested and worshiped on Saturday, but gradually switched to Sunday. One reason was the desire to distinguish themselves from the Jewish community that did not accept Jesus as Messiah. But the main reason was the realization that the resurrection of Jesus had changed everything and was at the very center of the Christian faith. The Sabbath, which had focused on the past— resting from the labors of the week just ending—became for Christians a forward-looking celebration of new life. Easter Sunday morning was the dawn of a new life, and every Sunday Christians celebrate the renewal of humanity and of the entire universe that took place through the death and resurrection of Jesus Christ.
Divine Mercy Sunday: Celebrating God's Merciful Love
In the Jubilee Year 2000, Pope John Paul II proclaimed that from that year forward the Second Sunday of Easter would be celebrated as Divine Mercy Sunday. This was proclaimed at the Canonization Mass of St. Faustina Kawalska, who worked throughout her life to make all aware of the merciful love of God. St. Faustina (1905–1938) was born and raised in Poland. Following a vocation to religious life, she was accepted by the Congregation of the Sisters of Our Lady of Mercy. As a member of the Congregation, she worked as a cook, gardener, and porter. In her spiritual life, her contemplation on the Mercy of God led her to develop a childlike trust in God and deep love for her neighbor.
When celebrating Divine Mercy Sunday, the faithful are called to reflect more personally on the graces won through the life, death, and Resurrection of Jesus Christ. In this way their hearts may be more fully aware of the mercy of God for them personally and for the sake of the world.