Ascension Day commemorates Christ's bodily ascension into heaven forty days after the Resurrection (Acts 1:1-11, Luke 24:50-53). The feast always falls on a Thursday — forty days counted inclusively from Easter Sunday. The observance is ancient. Augustine of Hippo (Ep. 54 to Januarius, c. 400) already regarded the Ascension as a feast of apostolic origin, placing it alongside Easter and Pentecost as celebrations 'which the whole Church observes throughout the world.' Eusebius of Caesarea mentions it in the early fourth century. The Ascension stands as the christological complement to the Incarnation: at Christmas, God descends to take human nature; at the Ascension, human nature is taken up into the life of God. The theological implications are enormous — our flesh, our humanity, is now at the right hand of the Father. The BCP 2019 lists Ascension among the seven Principal Feasts, giving it the highest possible liturgical precedence. The ten days between Ascension and Pentecost have traditionally been kept as days of prayer and expectation, recalling the disciples' waiting in the upper room (Acts 1:12-14). Some Anglican and Roman churches transfer the observance to the following Sunday, though the BCP 2019 does not explicitly authorize this practice.

The Ascension has shaped both the liturgical calendar and Christian architecture. The tradition of extinguishing the Paschal Candle after the Gospel reading on Ascension Day — symbolizing Christ's departure from visible presence — was widespread in the medieval West, though modern practice varies. Egeria records a vigil service at the Imbomon (the traditional site of the Ascension on the Mount of Olives) in the 380s, and the feast was well established in both East and West by the fifth century. In the Byzantine tradition, the Ascension is one of the Twelve Great Feasts, and its icon — Christ ascending in a mandorla of glory while the apostles gaze upward and angels announce his return — is among the most theologically rich in the Eastern iconographic tradition. The two men in white (Acts 1:10-11) who promise Christ's return connect the Ascension forward to the Second Coming, making it both a feast of accomplished salvation and eschatological hope. The collect in the BCP 2019 focuses on the ascent of hearts and minds: 'May our hearts and minds also there ascend, and with him continually dwell.' The season between Ascension and Pentecost — sometimes called the 'Great Novena' — is a period of prayer for the coming of the Spirit.

Helena was born around 250 in Drepanum in Bithynia (later renamed Helenopolis in her honor). Her social origins were modest — Ambrose calls her a stabularia, possibly 'innkeeper' — and she became the consort (possibly wife, possibly concubine — sources are ambiguous) of Constantius Chlorus, by whom she bore Constantine around 272.

When Constantius was elevated to Caesar in 293, he was required to set Helena aside in favor of a more politically advantageous match. Helena apparently lived in obscurity until her son gained power. After Constantine's victory at the Milvian Bridge (312) and his support for Christianity, Helena was elevated to the rank of Augusta — empress — and became a prominent figure at court.

She converted to Christianity (timing unclear) and was known for piety and charitable work. Around 326-328, in her late seventies, she undertook a pilgrimage to the Holy Land. Eusebius of Caesarea, writing within a few years, records that she founded the Church of the Nativity in Bethlehem and the Church of the Eleona (Ascension) on the Mount of Olives, and distributed alms generously to the poor, freed prisoners, and recalled exiles.

Helena died around 330 in her son's presence. Her body was brought to Rome, where her sarcophagus — an enormous red porphyry monument — survives in the Vatican Museums.

Traditionally, Helena discovered the True Cross during her Jerusalem pilgrimage. According to accounts that developed from the late fourth century onward (first clearly in Ambrose and Rufinus), Helena directed excavations at Calvary and uncovered three crosses. The True Cross was identified when a sick woman (or, in some versions, a corpse) was healed upon touching it. However, Eusebius, who is nearest to the events, does not mention the Cross discovery at all — a significant silence.