In the words of historian
Robert Barlett, "the natural consequence of
adopting a day for Jesus's birth was the ability to calculate a day for his conception nine months earlier, and so, as 25 December became generally accepted as the date of Christmas, 25 March rose into prominence too, and, just as Christmas had the added significance of being the old
winter solstice, so 25 March was the old
vernal equinox". The date of 25 March was chosen due to it being nine months before 25 December, and its association with the
spring equinox and the anniversary of
creation. The ancient
Babylonian calendar began around the spring equinox, in the month of
Nissānu, at which time they celebrated the
Zagmuk festival and recited their
creation myth, the
Enūma Eliš. Due to Babylonian influence, the beginning of the religious year in the
Hebrew calendar shifted to the spring equinox and the
Passover festival, with
Nisan being the first month. From the 3rd century, various Christian writers dated the anniversary of
the world's creation to the spring equinox. Creation was seen as a time of perfect equilibrium, and since day and night are equal on the equinox, this was linked to the separation of light and dark in the Genesis creation story. They also dated Jesus's
death or
resurrection to the spring equinox, partly because it was linked to the date of Passover and partly because the spring equinox was linked with new life and increasing light. In the Roman
Julian calendar, 25 March was the date of the
spring equinox. In AD 221,
Sextus Julius Africanus suggested that the spring equinox on 25 March was the date of Jesus's conception, and linked it to the anniversary of the world's creation. The
pseudo-Cyprianic work
De Pascha Computus, c.243, dates the first day of creation to the spring equinox on 25 March and dates Jesus's birth to 28 March, the anniversary of the
sun's creation on the fourth day. At first, the Feast of the Annunciation or Incarnation seems to have been celebrated on the Sunday before Christmas. The earliest evidence for a Feast of the Annunciation on 25 March is from the
sixth century. According to a letter of the emperor
Justinian I, the feast on that date originated with the church in
Constantinople around AD 555. A
Synod of Worcester, England in 1240 forbade all servile work on the feast. As this feast celebrates the
Incarnation of the Second Person of the
Trinity, many Church Fathers, including
St. Athanasius,
St. Gregory of Nyssa, and
St. Augustine, have expounded on it. ==Related celebrations==