CHRONOLOGY. — The study of historical sources (chronicles and documents) requires the historian and the diplomatist to verify the date given by the document or chronicle, with the twofold purpose of ascertaining the authenticity of the dating and of translating it into modern style (v. ANNO; ERA). If, for example, a document bears the date 1281, it may, after the appropriate verifications, turn out instead to belong to 1280 or 1282, according to whether the ab Incarnatione style was used in the Pisan or Florentine manner. Likewise, it indiction (v.) is correct and corresponds to the year, according as the Constantinopolitan or Bedean indiction is employed.
Dating by day, month, and year, as used today, was not always employed everywhere. Sometimes, for example, instead of the day and month, the name of a saint, the occurrence of a market, Easter Sunday, etc., was given; it may also happen that a document indicates, with an apparent scrupulousness of accuracy, even the day of the week. In such a case, it is necessary to ascertain whether, in that year, the indicated day of the week really coincided with the day of the month accompanying it: where this is not so, the discrepancy may constitute an indication of forgery. Elsewhere, instead of the year according to the Christian era, we may find the years of a sovereign’s reign. Here too it is necessary to verify which year, according to modern reckoning, the document belongs to, and whether that sovereign really reigned in that year, and so forth.
All questions of this kind are answered by chronology, or the art of verifying dates.
It is divided into two branches: the first, technical (chronography), which studies the use of the various types of calendar, the various eras, the various styles, and chronological computations for determining movable feasts, and provides the elements necessary for translating the chronological notation supplied by the document into modern style; the second, historical (chronistory), which provides lists of persons or events in strict chronological order.
Already in the Middle Ages great importance was attached to chronology, also for practical and religious reasons (v. COMPUTO ECCLESIASTICO); suffice it to recall the De temporibus and the De temporum ratione of the ven. Beda. In modern times chronology developed alongside diplomatics. Its first essays were Scaliger’s Opus de emendatione temporum (Paris 1583) and Petau’s Opus de doctrina temporum (there, 1633). But the principal treatise is the Art de vérifier les dates by the Benedictines M. d’Antine, C. Clémencet, and O. Durand, published in its 1st ed. in Paris in 1750 and subsequently revised and republished several times until 1844. More recent are the works of L. de Mas-Latrie, Dictionnaire de statistique religieuse (Paris 1851), and Trésor de chronologie (there, 1899). Among presentations of technical chronology, that of A. Giry (Manuel de diplomatique, there, 1894) deserves mention for its clarity and perspicuity. In Germany, the works of H. Grotefend (especially the practical Handbuch der historischen Chronologie, Hannover 1872, and the Taschenbuch der Zeitrechnung des deutschen Mittelalters
und der Neuzeit, 6th ed., there, 1928) and of E. Brinckmeier may be recalled. Among modern manuals are: F. K. Ginzel, Handbuch der mathematischen und technischen Chronologie (3 vols., Leipzig 1906–14); A. Cappelli, C., cronografia e calendario perpetuo (2nd ed., Milan 1930). Carmelo Trasselli