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 ... Lauds were not joined together as Matins Caesarius speaks of Prima, while the Gallicanum speaks of Ad secundum Caesarius distinguishes between Lucernarium and Ad Duodeciman, while ... 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 ...