CHRONOLOGY. – The study of historical sources (chronicles and documents) requires the historian and diplomatic scholar to verify the date provided by a document or chronicle, with the dual purpose of ascertaining the authenticity of the dating and translating it into modern style (v. ANNO; ERA). For example, if a document bears the date 1281, after appropriate verification it may prove to be instead 1280 or 1282, depending on whether the Pisan or Florentine style of dating ab Incarnatione was used. Similarly, one must determine whether the indiction (v.) is correct and corresponds to the year, according to whether the Constantinopolitan or Bedan indiction was employed.
The dating by day, month, and year now in use was not always employed everywhere. Sometimes, for instance, instead of the day and month, the name of a saint, the occurrence of a market, Easter Sunday, etc., might be given; it may also happen that a document, with apparent scrupulousness, indicates even the day of the week. In such a case, it is necessary to verify whether, in that year, the day of the week indicated actually coincided with the day of the month accompanying it; if not, the discrepancy may constitute an indication of forgery. Elsewhere, instead of the year according to the Christian era, we may find the regnal years of a sovereign. Here too it is necessary to verify to which modern year the document belongs and whether that sovereign actually reigned in that year, and so on.
All such questions 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 various types of calendars, eras, styles, and chronological computations for determining movable feasts, and provides the elements needed to translate the chronological notation given by a document into modern style; the second, historical (chronostoria), which provides lists of persons or events in strict chronological order.
Even in the Middle Ages, chronology was accorded great importance for practical and religious reasons (v. COMPUTO ECCLESIASTICO); suffice it to recall the De temporibus and De temporum ratione of the Venerable Bede. In modern times, chronology developed in tandem with diplomatics. Early examples include the Opus de emendatione temporum of Scaliger (Paris, 1583) and the Opus de doctrina temporum of Petau (ibid., 1633). But the greatest treatise is the Art de vérifier les dates by the Benedictine monks M. d’Antoine, C. Clémencet, and O. Durand, first published in Paris in 1750 and subsequently revised and republished several times until 1844. More recent works include L. de Mas-Latrie, Dictionnaire de statistique religieuse (Paris, 1851) and Trésor de chronologie (ibid., 1899). Among expositions of technical chronology, A. Giry’s Manuel de diplomatique (Paris, 1894) is notable for its clarity and perspicuity. In Germany, the works of H. Grotefend are noteworthy (especially practical is the Handbuch der historischen Chronologie, Hanover, 1872, and the Taschenbuch der Zeitrechnung des deutschen Mittelalters).
CHRONOGRAPH of the year 354 – Constantius II – Vatican Library, cod. Barber. XXXI, 39.
Source and principal documentation for knowledge of the ancient topography of Rome.