calendarium UK /ˌkælənˈdɛəɹi.əm/US /ˌkælənˈdɛɹi.əm/ noun1 •A calendar or timeline or events.Phoenician names occur in Suidas, Dioscorides, Apuleius, in martyrologies, calendariums, Acts of Councils, in Church Fathers (Augustine, Priscianus, Servus), &c. — 1865 formscalendaria · calendariums