Chronology

V

Political or Historical Time

Political chronology is determined by the dates and the sequence of events in human history. Most ancient nations related their history to the lifetime of some central figure or to the reign of a king. This system gave a fairly complete chronology of an individual's time, but the history of the nation was often unrecorded between the death of a king and the accession of his successor and by the omission of obscure or unpopular kings from the written records. As political chronology developed, historians instituted the use of so-called eras based on national, ecclesiastical, or scientific reasons, each era being dated from an outstanding event or a convenient date called the epoch of that era.

A

Middle Eastern Chronology

In ancient Mesopotamia, home of Sumer, Assyria, and Babylon, continuous chronology begins with the birth of King Sargon I (reigned about 2335-2279 bc), and a fairly complete list of kings has been compiled to the first dynasty of Ur, extending back to about 2670 bc and possibly earlier. Chaldean astronomers discovered the cycle that modern astronomers call the Saros, consisting of a period of 223 lunations (slightly more than 18 years) that is still important in the calculation of eclipses. According to various king lists, the chronology of ancient Egypt begins with the reign of Menes, who is listed as the first king of the 1st Dynasty. The start of his reign has been dated to around 2920 bc.bc The Egyptian year began with the rising of the star Sirius, but, as their civil year contained exactly 365 days, the Egyptians were compelled to use the so-called Sothic cycle, a period of about 1460 years from one time to the next, when the civil year coincided with the astronomical one. Such a coincidence occurred about ad140, but it is uncertain whether the first cycle started about 2780 or 4240 bc.

B

Greek and Roman Chronology

The era of the Olympiads of the Greeks was reckoned from July 1, 776 bc, and Greek astronomers introduced the Metonic cycle of 235 lunations (almost exactly 19 years) and also the Callippic cycle of 940 lunations (closer to 76 years). In Roman chronology the era of the founding of the city (ab urbe condita, or AUC) dates from April 22, 753 bc, and the Julian era dates from the reform of the calendar by Julius Caesar in 45 bc. In ad312 Emperor Constantine the Great introduced a cycle of 15 years called indiction.

C

Western Chronology

The Christian era, now used almost exclusively throughout the Western world for civil chronology, was first used in 525 by the Christian monk Dionysius Exiguus, who fixed the birth of Christ in the year of Rome 753. It is generally agreed that this date should have been fixed some years earlier. Dionysius's chronology was introduced into historical writings by Bede the Venerable in the 8th century.

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Scriptural chronology is extremely uncertain because various local chronologies were used at different times by scriptural writers, and different systems were used by contemporaneous writers. The Jewish Mundane era, beginning in 3760 bc, was not used until the 10th century ad. Jews now also use dates coinciding with those in the Christian era, but they treat the dates as belonging to a Common era and designate bc dates as bce and ad dates as ce. The creation was dated by the 17th-century Irish archbishop James Ussher as 4004 bc. The Muslim era dates from the Hegira, July 16, ad622, but because the Muslim calendar is based on lunar months and is of variable length, the reconciliation of its dates with those of the Gregorian calendar is very complicated.

The epoch of the Christian era is too recent to be a convenient reference point for technical calculations. The French classical scholar Joseph Justus Scaliger proposed in 1583 that the epoch of the Julian era be fixed at January 1, 4713 bc, at noon. The beginnings of the cycles used in antiquity coincided at that time, and the date was sufficiently remote to furnish a reference point to which all other chronological systems might be compared. The Julian cycle contains 7980 years of 365‚ days, but computation is seldom by years, and the days are numbered consecutively.

In many cases, astronomical chronology is used to verify or correct dates given in history for political events. For example, by reckoning backward, the time and place may be fixed for the occurrence of a remarkable eclipse, such as the eclipse reported by the Greek scientist Thales as causing the suspension of a battle between the Medes and the Persians. That eclipse was found to have occurred on May 28, 585 bc. Scottish history furnishes another instance: When King Håkon IV (the Old) of Norway sailed from Bergen with his Norse fleet to punish the king of Scotland, he landed in the Orkney Islands; there the sun appeared as a thin, bright ring. The British physicist Sir David Brewster found that an annular eclipse of the sun was visible in the Orkneys on August 5, 1263, about one o'clock. Such verifications in chronology depend on the testimony of contemporary writers or on information derived from inscriptions found on coins, medals, or monuments.

In the history of Western civilizations, the principal problems of chronology are encountered in the reconciliation of dates in the various calendars, such as the Julian, Gregorian, and Muslim. For example, an article appeared in the Edinburgh Courant of February 19, 1706. The article was an abridgment of one published in the London Gazette of February 13, 1705, which, in turn, was a translation from the Amsterdam Gazette of February 22, 1706. All three were published in the same week. The discrepancy in year was caused by the fact that Scotland and the Low Countries began the year on January 1, while England, until 1752, began it on March 25. The discrepancy in days was caused by the use of the Gregorian calendar in the Low Countries, at a time when England and Scotland still adhered to the Julian calendar.

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