Sunday is marked by three events: the beginning of Creation, the Resurrection, and Pentecost. On Green Sundays — the Sundays during the Time after Epiphany and the Time after Pentecost (unless a feast falls on one of these Sundays) — these three events are commemorated by the praising of the Three Persons of the Holy Trinity in this Preface of the Most Holy Trinity as the work of Creation is attributed to the Father, the Son rose from the dead, and the Holy Ghost descended on Pentecost. The Preface of the Holy Trinity originated in Spain and was brought into the Roman Missal by Alcuin (d. 804), court liturgist of the Emperor Charlemagne. Pope Clement XIII, in his decree of 3 Jan 1759, codified the use of this Preface on Green Sundays.
