Easter is the feast of the Resurrection of Jesus Christ from the dead — the oldest, highest, and most central celebration of the Christian year. Every other movable feast and fast is calculated from it; every Sunday is a weekly Easter. The date is determined by the Paschal computation established at the Council of Nicaea (325): Easter falls on the first Sunday after the first full moon on or after the vernal equinox (March 21), placing it between March 22 and April 25. The earliest Christians appear to have observed an annual Pascha from a very early period, though the precise origins are debated. The Quartodeciman controversy of the second century — whether to celebrate the Pascha on Nisan 14 (regardless of the day of the week) or always on a Sunday — attests that the observance was already widespread and deeply important by the mid-100s. Polycarp of Smyrna reportedly discussed the matter with Anicetus of Rome around 155 (Eusebius, HE 5.24), and the issue was sharp enough to prompt Victor of Rome to threaten excommunication of the Asian churches, a threat moderated by Irenaeus's famous appeal for peace. The Nicene resolution in favor of the Sunday observance became universal in the mainstream Church, though some groups maintained the Quartodeciman practice for centuries. The Great Vigil of Easter is among the most ancient liturgies in Christianity, with roots traceable to at least the third century (Apostolic Tradition). By the fourth century, Egeria describes an elaborate Jerusalem vigil with baptisms, and Augustine attests a similar pattern in North Africa.

The Great Vigil, which the BCP 2019 describes as 'the first liturgy of Easter Day,' begins in darkness. The Paschal Candle is lit from new fire — a symbol of Christ as the light of the world entering the darkness of the tomb. The Exsultet, the great hymn of praise to the Paschal Candle, is among the most magnificent pieces of Christian hymnody, attested from at least the fourth century (Ambrose may have composed an early version). The vigil readings trace salvation history from creation through the Exodus to the prophets, building to the proclamation of the Resurrection Gospel. Historically, the Vigil was the primary occasion for baptism — new Christians dying and rising with Christ through the waters, emerging to receive their first Eucharist on the night of the Resurrection. The BCP 2019 provides for baptism or renewal of baptismal vows at the Vigil. The Easter morning liturgy opens with the Paschal greeting: 'Alleluia! Christ is risen! / The Lord is risen indeed! Alleluia!' — a form attested across virtually every Christian tradition. The fifty days of Eastertide that follow (through Pentecost) are treated as a single unbroken feast — no fasting, no kneeling for prayer, Alleluias throughout. Easter eggs, the custom of which is documented from at least the thirteenth century, symbolize the sealed tomb and new life breaking forth. Easter is not a day but a season.

According to the Armenian historian Agathangelos, Gregory was born the son of Anak, a Parthian nobleman who assassinated the Armenian king Khosrov II. The infant Gregory was smuggled out of Armenia and raised as a Christian in Caesarea in Cappadocia, where he was baptized and educated.

As an adult, Gregory returned to Armenia and entered the service of King Tiridates III, seeking to atone for his father's crime. When Gregory refused to offer sacrifice to the goddess Anahit, Tiridates subjected him to prolonged torture and eventually threw him into a pit — Khor Virap ('deep prison'), near Mount Ararat — where he languished for thirteen years, sustained by a widow's secret supply of bread.

Meanwhile, Tiridates was afflicted with a mysterious illness (tradition describes him being transformed into a wild boar) that no physician could cure. His sister dreamed that only Gregory could heal the king. Gregory was brought from the pit, healed Tiridates (through prayer, not medicine), and the king was converted. Armenia officially adopted Christianity around 301 — a century before most of the Christian world.

Gregory was consecrated bishop by Leontius of Caesarea and systematically destroyed pagan temples and built churches across Armenia. He established his see at Etchmiadzin, where the cathedral he founded remains the spiritual center of the Armenian Church. After organizing the church, he withdrew to a hermitage and died around 331.

Gregory's descendants served as Catholicos (chief bishop) of Armenia for generations, establishing a hereditary ecclesiastical dynasty.

Traditionally, Gregory's thirteen years in Khor Virap were sustained by divine providence — a pious widow secretly brought him daily bread without anyone discovering her. His emergence from the pit, healthy and luminous, was taken as a miraculous sign. According to Agathangelos, Gregory had a vision in which Christ descended from heaven and struck the ground at Etchmiadzin with a golden hammer, marking the site of the mother cathedral.