Today is a religious rarity that will not occur again in our lifetimes. For most Christians in the West, it is Good Friday, the day of Jesus's crucifixion. It is also March 25, the traditional day of observing the Annunciation, when the angel Gabriel came to Mary and told her she would become pregnant with Jesus.
This overlap has happened just three times in the 20th century (1910, 1921, and 1932) and twice in the 21st (2005 and 2016). And it won't occur again until 2157.
It's a rare event because the Christians use different methods to schedule holy days. Fixed feasts, like Christmas (December 25 in the West) and the Annunciation (March 25), fall on the same day every year. And movable feasts, like Easter, fall on different days depending on the lunar calendar.
A March 25 Good Friday presents a tension for Christians: The Annunciation is a day of joy, when believers celebrate the beginning of Jesus's earthly life and Mary's enthusiastic embrace of her role as Christ's mother: "Behold, I am the servant of the Lord; let it be to me according to your word," she told the angel. But Good Friday is the darkest day of the Christian year — the day Christ was beaten, nailed to the cross like a common criminal, abandoned by nearly all of his friends and family, and killed.
Christians over the centuries have dwelled on the tension that a March 25 Good Friday presents. As Eleanor Parker outlines in a terrific post on her blog, the overlap of the Annunciation and Good Friday fascinated medieval artists. Here is a 14th-century illuminated manuscript that shows the crucifixion (on the left) next to the annunciation (on the right):
And when Good Friday fell on March 25 in 1608, John Donne wrote a poem, appropriately titled "Upon the Annunciation and Passion Falling upon One Day." He describes "this doubtful day / Of feast or fast, Christ came and went away."
The difficulty of honoring both days simultaneously is so great that whenever March 25 falls during the week of Easter, the Catholic Church pushes its Annunciation celebration to later in the year. (This year, the church's feast of the Annunciation is April 4.)
Still, as Parker points out, there's a richness in the "paradoxical conjunction of feast and fast." Even when Good Friday doesn't fall on March 25, it is mysterious and tension-filled for Christians. They mourn the death of Jesus but look forward to his resurrection just a few days later. They grieve his suffering but believe this suffering makes way for great joy: the salvation of the world.