From the witty, informed, perspicacious Fr. Z.:
In our traditional Roman calendar, Sunday is Quinquagesima, Latin for the symbolic “Fiftieth” day before Easter. This is one of the pre-Lenten Sundays which prepare us for the discipline of Lent.
The priest’s vestments are purple. No Gloria. No Alleluia. The prayers and readings for the pre-Lenten Sundays were compiled by St. Gregory the Great (+604).
The Consilium’s liturgical engineers under Annibale Bugnini and others eliminated these pre-Lent Sundays, much to our detriment. (Cf. BugniniCare).