The Solemnity is one of the oldest celebrations in the church and was first listed by the Council of Agde as one of the region's main festivals in 506 AD. Like many other major celebrations it was considered a day of rest and celebrated with three special Masses at dawn, midday and a Vigil. Before the 1969 calendar reforms it was considered a Double of the First Class with common Octave and took precedence over a Sunday should it happen to fall on one. Post 1969 the feast is considered a Solemnity. The Byzantine Rite celebrates the Feast on June 24th as a major feast day and is celebrated with an All-Night Vigil and single day Afterfeast. Professor Eamonn O Carragain, professor at the University College Cork writes:
By the sixth century, this solar cycle was completed by balancing Christ's conception and birth against the conception and birth of his cousin, John the Baptist. Such a relationship between Christ and his cousin was amply justified by the imagery of scripture. The Baptist was conceived six months before Christ (Luke 1:76); he was not himself the light, but was to give testimony concerning the light (John 1:8-9).
The date of the Solemnity likely lies in the Roman way of counting - counting proceeded backwards from the Kalends of the succeeding Month. An example would be Christmas - the eighth day before the Kalends of January (Octavo Kalendas Januarii) . The Solemnity was put on the eighth day before the Kalends of July but since June has only 30 days in the current calendar the feast falls on June 24th. While this the most likely explanation, it is also significant that the feast falls on the summer solstice due to Saint John the Baptist's words - He must increase but I must decrease.
In Tucson Arizona the day is celebrated as El Dia de San Juan and can be traced back to the Spanish Explorer Francisco Vasquez de Coronado who prayed for rain on June 24th, 1540. Immediately following his prayer, rain began to pour down from clouds overhead. In celebration, the people of followed morning mass on June 24th annually with an fully clothed immersion in the nearest water so that they could celebrate the baptisms Saint John performed in the Holy Scriptures. It is also fairly common to pluck herbs during the night of the feast - in Germany the herbs (Johanneskraut or Saint John's herbs) are brought to church for blessing.
he tradition of lightning fires on the eve of the feast can be traced back to the early twelfth century in a writing by the theologian Jean Belethus at the University of Paris. A monk of Lilleshall Abbey wrote in the 15th century:
In the worship of St John, men waken at even, and maken three manner of fires: one is clean bones and no wood, and is called a bonfire; another is of clean wood and no bones, and is called a wakefire, for men sitteth and wake by it; the third is made of bones and wood, and is called St John's Fire.
In England, the feast is one of the Quarter days of England. In Yorkshire it was custom for anyone who had moved into the parish the preceding year were to place a table outside their house with cheese, bread and beer for the enjoyment of anyone in the parish. It became a way for newcomers to meet others in the Parish and solidify their place in the community. In Ireland, children would solicit donations for the large bonfires to be lit several days before the feast - it was considered very bad luck to refuse them as the fires were used as a way to draw God's blessings on the summer crops. When the fires were lit, children would throw a bone into the fire and revelers would bring home spent embers from the fire to throw into their fields for good luck. Fishermen's boats were traditionally blessed by priests on the feast day. A famous poem, The Sisters, by Limerick poet Aubrey Thomas de Vere in 1861 describes Bonfire Night :
After our home attain'd, we turn'd, and lo!
With festal fires the hills were lit! Thine eve
Saint John, had come once more, and for thy sake
As though but yesterday thy crown were worn,
Amid their ruinous realm uncomforted
The Irish people triumph'd. Gloomy lay
The intermediate space; -- thence brightlier burn'd
The circling fires beyond it. 'Lo!' Said I,
Man's life as view'd by Ireland's sons; a vale
With many a pitfall throng'd, and shade, and briar,
Yet overblown by angel-haunted airs,
And by the Light Eternal girdled round."