Prime holds a unique distinction in liturgical history: it is the only canonical hour ever formally abolished by an ecumenical council. The Second Vatican Council's constitution on the liturgy, Sacrosanctum Concilium of 1963, reviewing an office it wished to restore to truthfulness of time, ordered in its eighty-ninth article that the hour of Prime is to be suppressed, and the 1971 Liturgy of the Hours carried out the sentence: the Roman books contain no Prime, and its useful residue, the martyrology reading, was left to be kept where desired.
The council's logic was straightforward. Prime duplicated Lauds, two morning offices within an hour of each other, and its origin as a monastic disciplinary measure gave it no claim on clergy and laity for whom the duplication was mere burden. The suppression, however, was Roman, not universal. The Byzantine cycle's First Hour, the equivalent office, continues wherever the Horologion is used, usually appended to orthros in parish practice. Monastic communities following older customaries, and communities using the 1962 Roman books under the successive permissions for the older form, still pray Prime daily.
The Anglican and Lutheran offices had absorbed its material centuries earlier. So the hour lives on around the edges of the communion that created it, a small case study in how liturgies die: not by forgetting, but by an explicit judgment that a form's founding purpose had lapsed, recorded in the acts of a council, with the hour's own history cited as the grounds.