The omissions are said at Lauds, Prime and Compline.
Are always used at Lauds, and give that hour its name.
It has already been indicated, by reference to Matins, Lauds, &c., that not only each day, but each part of the day, has its own office, the day being divided into liturgical "hours."
Matins and Lauds (about 7.30 A.M.); Prime, Terce (High Mass), Sext, and None (about 10 A.M.); Vespers and Compline (4 P.M.); and from four to eight hours (depending on the amount of music and the number of high masses) are thus spent in choir.
Beyond this we often find the calefactorium or day-room - an apartment warmed by flues beneath the pavement, where the brethren, half frozen during the night offices, betook themselves after the conclusion of lauds, to gain a little warmth, grease their sandals and get themselves ready for the work of the day.