The Nativity of St. John the Baptist
It is one of the oldest feast days in the Liturgy of the Church.
The only other births the Catholic Church celebrates as a feast are our Blessed Mother's and our Lord Jesus.
Why does the Church celebrate his birth? It is because he was "filled with the Holy Spirit even from his mother's womb." (Catechism of the Catholic Church No. 717) " It is also believed that Jesus sanctified him from the womb and removed his original sin.
Before John was born, the angel announced that "many would rejoice in his birth." Thus, his feast day is one of the more joyous feast in the Church calendar. In olden times, it was observed as a great holiday with much more rejoicing and celebrating than we do now. For example on the eve of his feast, many countries would light up mountains and hills with "St. John's Fires" "Scarce had the last rays of the setting sun died away, when all the world over, immense columns of flame arose from every mountain top, and in an instant every town and village and hamlet was lighted up." (Dom. P.L.. Gueranger).
"The Birth of St. John the Baptist"
Cappella Tornabuoni, Santa Maria Novella, Florence