"This Church, by letting these days join, hath shown
Death and conception in mankind is one."
From Upon the Annunciation and Passion Falling upon One Day 1608 by John Donne.
The two quotes from John Donne's poem about Good Friday falling on March 25 are taken from a larger article (which uses another line from the poem in its title) 'This doubtful day of feast or fast': Good Friday and the Annunciation, posted today by A Clerk of Oxford, a blog focused on medieval literature, history, and religion. The blogpost, which is well worth reading in full, can be accessed at: http://aclerkofoxford.blogspot.com/2016/03/this-doubtful-day-of-feast-or-fast-good.html
It happened as recently as 2005, but won't again until 2157 - this occurrence of Good Friday on the feast of the Annunciation. In much patristic and medieval tradition, at least since the 3rd century, March 25 - the date of the vernal equinox in the Julian calendar - was thought to be both the anniversary of the Annunciation (and therefore of conception of Christ, the Incarnation of the Son of God as Son of Mary) and of the Crucifixion. to quote A Clerk of Oxford, "traditionally the conjunction of the two dates was considered to be both deliberate and profoundly meaningful. The date of the feast of the Annunciation was chosen to match the supposed historical date of the Crucifixion, as deduced from the Gospels, in order to underline the idea that Christ came into the world on the same day that he left it: his life formed a perfect circle. March 25 was both the first and the last day of his earthly life, the beginning and the completion of his work on earth. … This day was not only a conjunction of man-made calendars but also a meeting-place of solar, lunar, and natural cycles: both events were understood to have happened in the spring, when life returns to the earth, and at the vernal equinox, once the days begin to grow longer than the nights and light triumphs over the power of darkness."
That represents the kind of spiritual and symbolic thinking that our ancient and medieval ancestors loved but which we spiritually and symbolically impoverished moderns increasingly find somewhat alien. Hence, horrible ideas like a fixed date of Easter have acquired a currency in our rationalistic, modern world which they would never have had for our ancient and medieval ancestors. As a medievalist, A Clerk of Oxford finds such a suggestion "rather depressing" - as should anyone who can at all appreciate spiritual and symbolic imagining! He sees in this a reminder of how the medieval Church "was in some ways immeasurably more humane and creative than its modern successors. It was happy to see human life as fully part of the natural world, shaped by the cycles of the sun and moon and the seasons; it was able to articulate a belief that material considerations, convenience, and economic productivity are not the highest goods, and not the only standards by which life should be lived. When confronted by calendar clashes with the potential to be a little awkward or inconvenient, the medieval church could have the imagination not to simply suppress them or tidy them away, but to find meaning in them - meaning which springs from deep knowledge of the images and poetry of scripture, the liturgy, and popular devotion."
Amen to that!