For decades, houses of worship have been consecrated by tidy congregations in their very best dress. Trim suits and ties pulled straight enough to choke the fidgety young parishioner were the norm, anything less being sure to draw the scorn of the flock.

But the culture has changed, and with it the Church. For some preachers and priests, word of this "new day" is written not in any holy book, but rather on the T-shirts young worshippers now wear to Sunday Mass. ...