The Church usually celebrates memorials and feast days of saints by commemorating the death of these saints, since the day of their death is also the day of their birth into everlasting life.
However, for our Lady, Jesus and John the Baptist, the Church celebrates their earthly birthday as well as the day of their death.
Thus, while we celebrate the earthly birth of John the Baptist on June 24, today we celebrate his heavenly birth into eternal life.
This feast day of the martyrdom of John the Baptist was already a celebrated phenomenon in the fourth century Church - a sign of its significance.
The Gospel of Mark narrates the unspeakable violence and cruelty inflicted on John the Baptist and the callous behaviour of Herod and everyone at the party. It was Herod's selfishness and aversion to the truth that brought about John's martyrdom; he was executed for witnessing to the truth.
The Gospel of John (1:19-34) has clearly noted that besides his ministry of baptism, John more importantly witnessed to Jesus, the coming Messiah. It was John's mission to prepare the way for Christ.
St John, help us to prepare the way for Christ, so that He may come ever more effectively into our lives.