By the term era is meant a period dating from a fixed point of time, generally some historical event, and used in reckoning years for chronological purposes. Historical eras are those on which historical chronology is based. A distinction can be made between eras of political or civic origin and those of religious origin.
Eras of Political or Civic Origin. To this class belong eras of empires, eras of cities or provinces, and eras of particular countries or regions.
Eras of Empires. The principal imperial eras are six in number and usually named after rulers or dynasties. The era of Alexander the Great has been made known through inscribed bricks and coins and was distinct from the era of the Seleucids. It began the first of Nisan, 330 b.c., and was connected with Alexander's capture of Persepolis (January 330).
The era of the Seleucids among the Greco-Syrians got its name from Nicator Seleucus, founder of the Dynasty of the seleucids, who instituted it to commemorate the beginning of his empire (312 b.c.). It was known also by other names: the era of contracts among the Jews, because of its legal character; the era of the Greeks or of Alexander among the Syrian Christians and the Arabs; the era of "the man with two horns," Alexander's epithet among the Arabs; the era of the Chaldeans or the Assyrians; the years of the Syro-Macedonians. The era was first employed in the lunar-solar calendar in use among the Macedonians that began with the first lunar month (ὁΔ[symbol omitted]ος, Dios) following the autumnal equinox. The beginning of the era was placed on Dios 1, 312 b.c. When the Greco-Syrians received from Rome the solar calendar with its fixed years of 365 days plus one day every fourth year, they fixed the beginning of the year and consequently that of the era as October 1, and later, c. a.d. 460, as September 1, in order to align it with the Byzantine indiction; but this did not affect the Oriental Syrians not subject to Constantinople.
The era of the Seleucids among the Persians began when the Seleucids, having become masters of Persia, imposed their era on it also, yet without changing its calendar, a solar one of 365 days without leap years that continued to proceed as it had before. The beginning of the era was placed on the first of Ferverdin (the first month of the year), which corresponded to Feb. 7, 311 b.c., of the Julian calendar.
The era of the Arsacids, named after Arsacius, the first King of the Parthians, was superimposed on the preceding era of the Persians with the same beginning of the year, the first of Ferverdin. It began on Ferverdin 1, 248 b.c., which corresponded to January 22.
The era of Yezdegird was a continuance of the preceding era and of the same type, having as its point of departure Ferverdin 1 (June 26), a.d. 632. The Jalalaean era ended the era of Yezdegird and was the result of a reform that substituted a fixed solar calendar for the previous one that did not have leap years. The beginning of the year was placed at the vernal equinox, which, being then the 19th of Ferverdin (March 15, 1079, of the Julian calendar), was changed to the first of Ferverdin.
Eras of the Cities or Provinces. Some eras were connected with certain cities. The most important of these were the following.
The era of the Olympiads was named after the city of Olympia, where the Olympic games were held every four years. Each period of four years, at the end of which the games took place, was called an Olympiad. Chronographers, several centuries later (c. 300 b.c.), got the idea of using these four-year periods as a measure of chronology. The era of the Olympiads reckoned not directly with individual years, but with the series of four-year periods starting with the institution of the games. The point of departure was the beginning of July 776 b.c. In the concordance tables, the beginning of the year is placed at the beginning of the July that follows January 1 of the corresponding Dionysian year.
The era of the foundation of Rome (Urbis conditae, abbreviated u.c.), commonly employed, was determined by Varro (De gente populi romani, written c. 43 b.c.). It began in 753 b.c. and was reckoned as starting on January 1, even though April 21 was regarded as the actual date of the founding of the city. The Capitoline era was another era based on the traditional founding of Rome. It was established according to the tables of the consuls engraved at the Capitol c. 30 b.c. and is one year behind the years of Varro's era. It appears in certain inscriptions and in the works of a few authors.
The Actian era was common to several cities and provinces. It was connected with the victory of Actium, which took place on Sept. 2, 31 b.c.; but in it the beginning of the year varies according to the different calendar (see below).
Egyptian Eras. In Egypt three different eras were in use: the Diocletian, the Alexandrian, and the Oxyrhynchus era (the last variously dated).
The era of Diocletian (also called the era of the martyrs) was common to all of Egypt. Its point of departure was Thoth 1, a.d. 284. In three years out of four, Thoth 1 was August 29; but every fourth year, i.e., in the year after the leap year, it was August 30. (On its origin, see chronology, medieval.)
The Alexandrian era was an Actian era of which the beginning was fixed on Thoth 1, 30 b.c. Thoth 1 was either August 29 or August 30, as above. The Thoth 1 with which this era began was Aug. 30, 30 b.c. This date also inaugurated the replacement of the Egyptian calendar having 365 days every year with one having 366 days every fourth year.
As for the eras of Oxyrhynchus, as many as eight of these have been noted, of which two are of more importance: a.d. 324, the year Constantius II became emperor, and 355, the year Julian became emperor.
Eras of Syria, Palestine, and Arabia. These include the era of the Seleucids, the Actian era, and the era of the province of Arabia.
The era of the Seleucids was the same as the imperial era mentioned above as common to Syria, Palestine, and Arabia.
The Actian era was common to several cities: Tripoli, Seleucia of Pieria, Laodicea, and Gerasa. Its year began October 1.
The era of the province of Arabia, or the era of Bostra (the capital), commemorated the Emperor Trajan's establishment of Arabia as a province. Its point of departure was March 22, a.d. 106, the vernal equinox falling on that day at that time and thus marking the beginning of the year.
Local Eras. A good number of the local eras commemorated the granting of autonomy to various cities, either by Pompey or Caesar, and for that reason are called Pompeian or Caesarean; their starting dates depend on when these cities received their independence.
Pompeian eras were used in various cities of Syria and Transjordan, especially in the cities of the decapolis: Abila, Antiochia ad Hippum, Kanatha, Dium, Gerasa, Gadara, Philadelphia, and Pella. The starting date for Gadara was 64 b.c.; for Philadelphia (Ammān), 63 b.c. For the other cities the dates are uncertain, between 64 and 61. Cities outside the Decapolis began their eras about the same time: Antioch and Apamea in 66 b.c.; Demetrias of Phoenicia and Dora in 63; Arethusa in 64 or 63; Epiphania of Cilicia in a year that is uncertain; Gaza on Oct. 28, 61 b.c., following the introduction of a fixed year—an era in use until the 7th century; Tripolis in 64–63; and Scythopolis in 64–63 b.c.
Caesarean eras, with their starting dates, were used in the following cities: Laodicea, Dios (later Oct.) 1, 48 b.c.; Ptolemais, 47; Gabala, Oct. 1, 47 or 46; Antioch (the most important of all), Dios (later Oct.) 1, 49 (Sept. 1, following the adjustment to the Byzantine indiction, c. 460); several Syriac writers begin this era Oct. 1, 48 b.c.
Other local eras were used in other cities in Syria and Palestine that had eras of their own: Ascalon, two eras— 104 and 57 b.c.; Beirut, 81 b.c. (under Tigrane); Eleutheropolis, a.d. 200; Laodicea, besides the Actian and Caesarean eras already indicated, three other eras—era of freedom under Tigrane, 81–80 b.c.; era of its establishment as a metropolis, a.d. 194; era of the colony, a.d. 197–198 [the last was recently discovered by H. Seyrig, Syria 40 (1963) 30–32]; Ptolemais (Accho), besides the Caesarean era indicated, had another era, 174 b.c. (the year of the establishment of the Antiochian colony in the city); Seleucia of Pieria, 109 b.c.; Sidon, 110 or 109 b.c.; Tyre, two eras, 274 and 116 b.c. (independence of the city); the beginning of the year, following the adoption of a fixed year, was October 19.
For Bithynia and Pontus there were the era of the independence of Bithynia, beginning in 297 b.c., and for several cities—Apamea, Myrlea, Bithynium, Nicaea, Nicomedia, Prusa—an era that began in 283 b.c., and came to an end when Bithynia became a Roman province.
In the proconsular province of Asia the era of Sulla, conqueror of the province, began autumn 85 b.c. and was fixed at the equinox, September 24, following the adoption of the solar calendar, later at September 23, the dies natalis of Augustus. This era appears in inscriptions from Phrygia, Mysia, Lydia, Pisidia, and Lycia. It continued up to the 6th Christian century.
The era of Galatia, beginning in 25 b.c., was employed in Ancyra, Pessinus, and Tavium.
The era of Pontus Polemoniacus was employed in several cities including Trabezus, Cerasus, Neocaesarea, and Zela. It began October 64 b.c.
Local eras were in use in several of the principal cities: Adana (Antiochia ad Sarum), sometime shortly after 19 b.c.; Amasia, October 3 b.c., annexation to the Roman Empire; Amisus, October 32 b.c., liberation; Anazarbus, 19 b.c.; Gangra, 5 b.c.; Comana, a.d. 34 or 35; Mopsuestia, 68 b.c.; Pompeiopolis, 7 b.c.; and Sinope, which had two eras, 70 and 45 b.c.
Eras of the Balkan Peninsula and the West. Several regions in the Balkans and in western Europe had their own eras.
The era of Upper Moesia began Jan. 1, a.d. 239, when the region was made a Roman province.
The era of Dacia dates from a.d. 246, after the middle of the summer.
Macedonia had two eras—one starting at the time of the Roman conquest, autumn 146 b.c., following the adoption of the solar calendar, the beginning of the year being fixed at October 15; the other an Actian era, beginning Oct. 15, 32 b.c. These two eras are frequently joined in the inscriptions.
The Spanish era began on Jan. 1, 38 b.c. It is found in inscriptions and was current with the chroniclers on the peninsula. It was used in Spain as late as the 14th century and in Portugal until 1422, when it was officially abandoned. It was in use also in the Visigothic provinces of southern Gaul. Its origin has not yet been explained.
The era of Mauretania (Caesarean, Sitifian; for Tingitane Mauretania evidence is lacking) began Jan. 1, a.d. 40, and dates from the annexation of Mauretania by the Roman Empire.
The Carthaginian era is indicated in several inscriptions by the formula anno N. Kartaginis. It is now known that the era was connected with the capture of the city by the Vandals in a.d. 439, and not, as was once thought, with its reconquest by the Byzantines. There is no certain evidence for any era connected with this reconquest.
Eras of Religious Character. Certain eras were established with a starting point connected with important events in the histories of various religions. The most important of these are the following.
Era of Abraham. This is used in the Chronicle of Eusebius. It begins with the call of Abraham. The birth of Christ is placed by Eusebius in the year 2015 of this era, 2,014 years after the call of Abraham, two years earlier than in the modern common era, which places it in 2017 of this era; therefore, the era of Abraham begins in 2016 b.c. But this relationship is not constant; it can be shown by cross comparisons that there is a deviation of two years in the calculations of Eusebius from the year 2210 of this era (a.d. 192) to the end of 2343 (a.d. 326), which moves the beginning of his era back from 2016 to 2018 b.c. In St. Jerome's continuation of this era from 2343 to 2395, the deviation is only one year, which brings the beginnings of the era to 2017 b.c.
Christian Eras. Several eras have been established by Christians beginning either on a computed year as the time when the world was created or on a year in the life of Christ.
The Alexandrine, or mundane, era began in the year 5492 b.c., which is considered to have been the year in which the world was created. In this era the year 5501 marks the birth of Christ, which is a starting date also for a Christian era frequently used in conjunction with this world era. The last two digits of any date are the same and always constant in both cases; thus, in this era the year 5965 of creation is the year 465 after the birth of Christ. Since the Alexandrine world era is eight years behind the modern common era, the same is true of its accompanying Christian era. Consequently, the year one in the latter era is a.d. 9 in the Christian. The beginning of its year is the same as that of the world era, i.e., March 25, which marks both the creation of the world and the Incarnation of Christ.
In the Proto-Byzantine era the 1st year was 5509 b.c., and the birth of Christ was placed in the year 5507 (3 b.c.); but this date of the birth of Christ was not used for chronological purposes.
The Byzantine era begins with the creation of the world considered as having taken place in 5507 to 5508 b.c. But Byzantine authors were not uniform in regard to the year of the birth of Christ. At least five different dates can be noted. The principal chronicler (Skilitzes-) Cedrenus placed Christ's birth in 5506 of this era (3–2 b.c.) on December 25 (3 b.c.) and constructed an era of Christ in conjunction with his mundane era, computing it as beginning with the Incarnation on March 25, 5505, of the mundane era, so that the final figure differs by six between the two eras, e.g., the year 5950 of the mundane era is the year 456 of his Christian era.
The common Christian era is known also as the Dionysian era because it was first used by dionysius exiguus in his paschal table as a substitute for the Diocletian era. The era begins on January 1 of the year of Christ's birth. This year is situated chronologically by its relationship to the Diocletian era in the paschal table mentioned above, in which the year 532 of the Christian era corresponds to the year 248 of the Diocletian era. The Dionysian era spread abroad little by little —first in England, where it was brought by St. Augustine of Canterbury, then in France, and finally in the rest of Europe. It was commonly used by chroniclers in the West from the time of Bede, except in the Iberian Peninsula, where the chroniclers retained the Spanish era for a long time. The beginning of the year differed from place to place: December 25, March 1, Easter, or January 1. By the end of the 16th century January 1 was commonly accepted as New Year's Day in this era, following the example of France, where it was made official in 1563.
The era of the Ascension, found among the Greeks and the Syrians, began in a.d. 31.
Jewish World Era. This era began on the first of Tishri 3761 b.c. Its invention appears to go back, at the earliest, to the latter half of the 4th Christian century.
Islamic Era or Era of the Hijra. Year one of this era began on the 1st of Moharem (1st month of the Muslim year), July 16, 622, marking the day arbitrarily set for the commemoration of Muḥammad's hijira, or flight from Mecca to Medina; the flight actually took place 68 days later. The era was instituted by Caliph Omar. It has been in continuous use by Christians living under Muslim rule (in Egypt, Syria, Iraq, and Persia), as well as by the Muslims. Since the Muslim year consists of 12 lunar months totaling 354 or 355 days, special tables must be used for converting a date in the Islamic era into a date in the Christian era. (see calendars of the ancient near east.)
For eras of cyclic origin that, though without historical basis, were nevertheless commonly used in daily life and by the chroniclers, see chronology, medieval, 1.
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"Eras, Historical." New Catholic Encyclopedia. . Encyclopedia.com. (August 15, 2018). http://www.encyclopedia.com/religion/encyclopedias-almanacs-transcripts-and-maps/eras-historical
"Eras, Historical." New Catholic Encyclopedia. . Retrieved August 15, 2018 from Encyclopedia.com: http://www.encyclopedia.com/religion/encyclopedias-almanacs-transcripts-and-maps/eras-historical