Ad Duodecimam

Gallican Rite - The Divine Office
... There were two principal services, Matins (Ad Matutinam, Matutinum) and Vespers (ad Duodecimam, ad Vesperas Lucernarium) and four Lesser Hours, Prime, or Ad Secundum, Terce, Sext, and None and ... Matins Caesarius speaks of Prima, while the Gallicanum speaks of Ad secundum Caesarius distinguishes between Lucernarium and Ad Duodeciman, while Aurelian distinguishes between Ad Duodeciman ... The Council of Tours orders six psalms at Sext and twelve Ad Duodecimam, with Alleluia (presumably as Antiphon) For Matins there is a curious arrangement which reminds one of that in the Rule of St ...