PM5502: Concerning Chronology

In General

The term chronology has two meanings:

  1. An account of the past history of a particular subject, making reference to the time frames involved. For example, the attempt to assign approximate dates to the events of the Bible is Biblical chronology.
  2. A system which lets us assign numbers to particular years.

In the later sense, the most common system of chronology today is the A.D. / B.C. system. A.D. comes from Latin for Anno Domini (Year of the Lord), B.C. meaning "Before Christ". In this system, there is no year zero: 1 B.C. is followed immediately by 1 A.D. with no year zero intervening. (A related system used by astronomers, "astronomical year numbering", has a year zero, and negative years before that - but its years are offset by one from B.C. years, since -1 = 2 B.C.)

The A.D. system was invented by the 5th century author Dionysius Exiguus. He was compiling tables to ease the calculation of the date of Easter. At the time, years were most commonly expressed in Anno Diocletiani - years since the start of the reign of the Roman Emperor Diocletian. This was the usual system of chronology in the late Roman Empire, and had been continued by Christians - despite the fact that Diocletian was a notorious persecutor of the Christian church. But Exiguus did not want to use a system which acknowledged a persecutor, so he invented A.D. dating as an alternative. He based its start on the estimated year of Jesus' birth - although, modern scholarship believes he was out by a few years. The A.D. system proved popular with Christians, and soon the Anno Diocletiani system was abandoned in the West. (In the East, it was a different story - Egyptian Christians retain to this day the old Anno Diocletiani system, while Greek Christians moved for a while to an A.M. system instead, before eventually settling on A.D. more recently - see more discussion below.)

Due to the expansion of European powers in the modern period, the A.D. system has come to been adopted for secular use by most of the countries in the world, including by most non-Christians. As a result, some have objected to its naming, and have suggested the names C.E. and B.C.E. instead of A.D. and B.C. These proposed terms intentionally have a dual expansion - either "Common Era" or "Christian Era", as one prefers. Many academic texts and textbooks have adopted C.E./B.C.E. instead of A.D./B.C. Others however oppose this recent innovation - many Christians see it as an attempt to obscure the Christian origins of our dating system. Some non-Christians feel the same way - if using a Christian dating system is bad, then renaming it to hide its Christian origins isn't really fixing things.

There are many other systems of chronology that exist. Just as A.D. is dated from a significant date in the Christian religion, some other chronologies choose a start date significant in the other religions:

  • Muslims use Anno Hegirae (A.H.) - years since the flight of Muhammad from Mecca (the Hijra) in 622 A.D. This is more than just a difference in start date, since the Islamic year is shorter than the Gregorian one.
  • Jews traditionally use Anno Mundi (A.M.) - years since Creation. The base date of A.M. assumes the world was created in 3760 B.C. The Byzantine Empire used to use a different A.M. chronology, which dated creation to 5509 B.C.
  • Many Buddhists use "Buddhist Era", dated from the birth of the Buddha - although there are different dates for Buddha's birth, and hence different Buddhist chronologies
  • The later Roman Empire used Anno Diocletiani, from the ascension of the Emperor Diocletian in 284 A.D. Christians also used this date system, prior to the adoption of A.D., despite being named for an infamous persecutor of Christians. Coptic Christians still use this calendar, but name it the "Era of Martyrs" instead, since Diocletian began arguably the greatest persecution of Christians in history.
  • Earlier, the Roman Empire and Republic used Ab urbis condita (AUC) dating from the believed founding of the city of Rome, in 753 B.C.
  • The Saka Era, traditionally used by Hindus, begins with the reign of the Saka dynasty in 78 A.D.
  • The Julian Era is an artifical construction invented by the historian Joseph Scaliger, who disliked how A.D./B.C. dating requires the use of two different dating systems for historical dates. He chose as a starting point 4713 B.C., since he believed all historical dates were subsequent to that. It has never seen much use by historians, but it is used in astronomy.
  • The scientist Cesare Emiliani has proposed a Holocene Era, starting in 10,000 B.C. The motivation is the same as the Julian Era - to make all historical dates fit in a single system - but it is easier to convert to/from the A.D./B.C. system than the Julian Era is.

Choice of chronology is a separate but related issue from choice of calendar - chronology determines how to number the years, calendar where the years start and end and how to subdivide them. So, the A.D./B.C. system is used with both the Gregorian and Julian calendars - although their years are slightly different in length, the discrepancy makes little difference except when dealing with the very distant future. By contrast, the Islamic calendar uses a significantly different year length from the Gregorian/Julian, so the difference between A.H. and A.D. dates keeps on growing.

A criticism of the Common Era system is that it leaves much of history in BCE dates, and for added confusion lacks a year zero. There have been several suggestions to pick an earlier starting point, which would enable a single system to address all of history. Joseph Scaliger proposed Julian Era dates, from 4713 BCE. Another proposal, by Cesare Emiliani, is the Holocene Era, with an epoch of 10,000 BCE. This has the advantage that the arithmetic for conversion is far more straight forward than Julian Era: 2011 CE = 12011 HE.

In Maratreanism

  • Maratreanism prefers the use of the terms CE/BCE to AD/BC
  • However, Maratreanism prefers the use of the Maratrean Era (ME), according to which 2011 CE = 34011 ME
  • It must be asked, why that epoch? This is a matter revealed from heaven; we must accept it without explanation. It need not necessarily be thought as an epoch of the Travancine-Clarettan era; it might be, but then again it might be not; such a matter has not been revealed to us