The Horologion (Greek: Ὡρολόγιον; Church Slavonic: Часocлoвъ, Chasoslov, Romanian: Ceaslov) or Book of hours provides the fixed portions (Greek: ἀκολουθίαι, akolouthiai) of the Divine Service or the daily cycle of services as used by the Eastern Orthodox and Eastern Catholic churches. Into this fixed framework of the services, are inserted numerous parts changing daily.