KELLNER, KARL ADAM HEINRICH. — Patrologist and liturgist, born at Heiligenstadt am Eichsfeld (Prussian Saxony) on 26 Aug. 1837, died at Bonn on 6 Jan. 1915. After ordination to the priesthood, he devoted himself to pastoral care, then became professor of theology at the Seminary of Hildesheim (1867–74) and, from 1882 until his death, professor of patrology, liturgy, and catechetics at the University of Bonn.
Among his writings, notable are his edition of the works of Tertullian (1882) and Ausgewählte Schriften des Sept. Tertullianus (2 vols., 2nd ed., 1912). His most celebrated work is Heortologie oder das Kirchenjahr und die Heiligenfeste in ihrer geschichtlichen Entwicklung, which went through three editions (Freiburg in Br. 1900, 1906, and 1911; Italian trans. by A. Mercati, L'anno ecclesiastico e le feste dei santi nel loro svolgimento storico, 2nd ed., Rome 1914). This work met with the most favorable reception (cf., e.g., Analecta Bollandiana, 21 [1902], p. 95). In it, K. collected and critically examined a vast body of material on the history of the liturgical year and its principal feasts, employing a rigorous method.