I noted on the actual — that is to say, observed (by the Holy Church of Rome) — Feast of Saint Thomas Aquinas on January 28, 2022 and 2021, that that date is not the one on which the Angelic Doctor entered upon his eternal reward, but the date when his relics were transferred from the Benedictine monastery of Fossa Nova in Italy, to the Dominican convent in Toulouse, France. The date of his death is today, March 8, and until the reform of the General Roman Calendar after the Second Vatican Council, this was the day on which the Universal Church celebrated his Feast Day and Sainthood. In 1969, Pope Paul VI issued a reformed calendar of saints’ feasts and moved that of Saint Thomas (among others), it is believed, to allow Lent to retain a more penitential tone without being interrupted by the celebration so many saints, especially that of so important a Doctor of the Church. In turn, this allowed Thomas’s feast to be celebrated apart from the penitential air of Lent.
I think there are some Catholics and devotees of Saint Thomas who consider March 8 to be the real Feast Day of Saint Thomas Aquinas, and continue to celebrate it, even though it falls in Lent, and even though the pope moved it to February 28 over 50 years ago. But Saint Thomas himself was ever the faithful son of the Church, and would have, and indeed did, defend the prerogative of the Church to set the celebration of feasts, as these are not Divine institutions and actual instruments of grace as the Sacraments are. As such, they are left to the discretion of the Church.
But in the sacred things [wherein] no grace is given: for instance, in the consecration of a temple, an altar or the like, or, again, in the celebration of feasts. Wherefore Our Lord left the institution of such things to the discretion of the faithful, since they have not of themselves any necessary connection with inward grace.Summa Theologiae I-II, q. 108, a. 2 ad 2, emphasis added.
It is, I believe, good to be dispensed from penitential practices on Feasts and Solemnities during Lent, as we do for the Solemnities of Saint Joseph and the Annunciation, when we even go so far as to use the regular Gospel acclamation (the A-word) and sing the Gloria at Mass, for these feasts remind us of God’s mercy and the joy of heaven to which we are called, and for which the penances of Lent are meant to prepare us.
Nevertheless, I encourage you to redouble your Lenten sacrifices on this non-feast day of Saint Thomas, and practice extra mortification as an act of obedience and fidelity to the liturgical authority of the Holy See to institute and move the celebration of feasts. It’s what Saint Thomas would want, I believe.
Unless, of course, you have a special devotion to Saint John of God, whose optional memorial is celebrated on March 8. Then, rejoice with that saint.