This weekend we celebrate the Nativity of St John the Baptist. Dating back to the 4th century, this feast is now observed annually on June 24, and this year it happens to fall on a Sunday, preempting the 12th Sunday of Ordinary Time. The Nativity of St John the Baptist has its own Vigil, so the readings and prayers for Saturday evening will be different than Sunday morning.
In liturgical terms, a 'nativity' is not a birthday, but a birth. Today is not John's birthday. Today John is born! His message of repentance and conversion is the same for us today as it was 2000 years ago.
Today is not a celebration so much of the announcement of John's birth, but the naming of John and his special role in salvation history. John preached a difficult message that demanded metanoia, a turning around of one's life.
Those who preach a difficult message usually have to pay a large price, in John's case, his life. He reminds us that we are to give our everything, lay it on the line, to be disciples of Christ.