Note: The arrangement of liturgical feasts appearing on this calendar, and that of the Ordo Missae Celebrandae et Divini Officii persolvendi in use at the Oratory of the Immaculata, differs at times from that of the General Roman Calendar (Calendarium Romanum Generale) because it has been adapted from the traditional Breviarium Monasticum Pro Omnibus Sub Regula Sancti Patris Benedicti Militantibus and the Missae Propriae Ordinis Sancti Benedicti supplement to the Missale Romanum.