Sometimes we take the simplest things for granted – isn’t it obvious that we celebrate Mass on a Sunday? But is it obvious? Didn’t the Lord celebrate the first ever Eucharist on a Thursday? And in the evening? So why, from the earliest times, have Christians celebrated the Lord’s Resurrection with a Eucharist on Sunday morning?

Those days when we do something different – like today – help us to understand the logic behind the rule. You see, today instead of the Second Sunday after Pentecost (‘Pentecost II’) we celebrate the ‘External Solemnity’ of Corpus Christi, the Feast which occurred the previous Thursday. It only happens with feasts that may occur on a weekday – such as Corpus Christi (which is always the Thursday after Trinity Sunday); or the Most Sacred Heart of Jesus (whose prescribed day is the Friday after the (former) Octave of Corpus Christi). It also happens with the Feast of SS. Peter and Paul – celebrated on June 28th – and for all local Patronal Feasts. This liturgical hopscotch is not simply to keep you guessing on a Sunday morning.

The green Sundays (unhelpfully and inaccurately translated ‘Ordinary Time’ in the Novus Ordo) are themselves a way of repeating the celebration of Easter throughout the year: a little Easter. In the Novus Ordo these ‘little Easter’ Sundays are actually counted per annum – that is throughout the year, whereas in the Vetus Ordo, they are counted from the Epiphany and Pentecost respectively, but they represent the settlement of a dispute in the early Church – should we celebrate Easter every week or just once a year? The answer was: both. At a later date, celebrations of the Eucharist began to happen on the memorials of martyrs between the Sundays – until finally, the Church discerned that celebrating a ‘little Easter’ every single day was a spiritual benefit and daily Mass was instituted. It was not so from the beginning – but we are glad for the development.

So why the Thursday ‘meal’ on a Sunday then? Well, the fact that the Lord instituted the Eucharist as the means to experience the Paschal Mystery shows us that the Mass was never, ever about re-enacting the Last Supper. It if were – then the Mass would intrinsically be an evening function – whereas it is intrinsically a morning function, only by indult celebrated after Noon. That Supper was a vehicle for us to inhabit the mystery of the Lord’s Passion, Death and Resurrection: the Triduum rolled into one.

The only time Thursday is remotely important is on the two days instituted by the Church to memorialize the institution of the Eucharist itself: Maundy Thursday and Corpus Christi. In other words, since we always use the Thursday template to celebrate the Sunday victory: every Mass is a “Thursday-Sunday” whereas Maundy Thursday and Corpus Christi are “Sunday-Thursdays.” So what’s an external solemnity then? Well, it’s a “Sunday-Thursday-Sunday.” Happy Feast!