Q: This year the Solemnity of the Nativity of John the Baptist falls on the day after Corpus Christi. Are we free to celebrate John the Baptist at a Sunday night mass on June 23?
A: I’m sticking with what I posted here: https://paulturner.org/solemnity-of-mary/
But it appears that the Paulist Ordo and the USCCB disagree with me. The Ordo says, “For pastoral reasons, the Vigil Mass of the Nativity of Saint John the Baptist may be celebrated this evening.” And for June 24, the USCCB tells you which readings are for the Vigil, even though it is silent about the Vigil option for Sunday night
But I hold that since the day of precept is Sunday, not Monday, that the Sunday mass must be offered for the benefit of the faithful.