The interpretation timeline
The institution of Corpus Christi
First kept at Liège, the feast was extended to the whole Church by Urban IV; Aquinas composed its Office.
1246 · 1264
Liège · Orvieto
Scholastic
c. 1100 – 15001246
Event
The feast of Corpus Christi
First kept at Liège in 1246, the feast of Corpus Christi is extended to the whole Church by Pope Urban IV in 1264 (the bull Transiturus); St. Thomas Aquinas composes its Office — the hymns for the hours and the sequence for the Mass.
Modern · 1953 →
The in-app commentary runs from the Fathers to the early-modern record, then stops — that's where the public-domain sources end, not where the reading does. For the modern reading, follow the sources directly.