Today is the Feast of St. John the Baptist. June 24th is three months after the Feast of the Annunciation, because in the Gospel story Gabriel told Mary that Elizabeth was six months pregnant with John, and also June 24th is six months before Christmas. As one source that I read indicates, the purpose is not to pinpoint exact dates but to interrelate these scriptural narratives in a liturgical way. This feast is also notable because it honors John’s birthday rather than (like nearly all other feast days) the day of the remembered person's death. This site provides some of the Roman Catholic theology, and also links this feast day to pagan celebrations of the Summer Solstice a few days ago.