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(General) Chronology is the science of locating events in time. An arrangement of events, from either earliest to latest or the reverse, is also called a chronology or, particularly when involving graphical elements, a timeline or a living graph. See also Chronicle.

Contents 1 Definition 2 Calendar and Era 3 Anno Urbis Conditae Era 4 Astronomical Era 5 Other chronological subjects 6 Prehistoric chronologies 7 See also 7.1 Examples 7.2 Techniques 7.3 Other 8 References 9 Further reading 10 External links

Unlike chronometry (i.e. timekeeping), which is part of physics, (general) chronology, as the science of locating historical events in time, is part of the discipline of history.

A chronology may be either relative—that is, locating related events relative to each other—or absolute—locating these events to specific dates in a Chronological Era. In that these dates are themselves events, the difference between the two blurs a little: an absolute chronology just includes a strange sort of event called a date which is common to all absolute chronologies covering the same period of time. Even this distinction may be blurred by use of different calendars. In Judeo-Christian cultures, historical dates in an absolute chronology are understood to be referred to the Christian era, in combination with the (proleptic) Julian calendar (originally) and the Gregorian calendar respectively.

The familiar terms ‘calendar’ and ‘era’ (within the meaning of a coherent system of numbered calendar years) concern two complementary fundamental concepts of chronology. For example during eight centuries the calendar belonging to the Christian era, which era was taken in use in the eighth century by Bede, was the Julian calendar, but after the year 1582 it was the Gregorian calendar. Dionysius Exiguus (about the year 500) was the founder of that era, which is nowadays the most widespread dating system on earth.

Though in Roman antiquity one frequently reckoned back to any supposed year of foundation of the city of Rome, the Anno Urbis Conditae era, which like the Anno Domini era did not in reality exist yet in antiquity, was used systematically for the first time only about the year 400, namely by the Iberian historian Orosius; pope Boniface IV (about the year 600) seems to have been the first who recognized the connection between these two eras (i.e. AD 1 = AUC 754).

AUC commonly does not stand for Anno Urbis Conditae/ the year of the foundation of the city, but ab urbe condita/ since the foundation of the city (rome).

Dionysius Exiguus’ Anno Domini era (which contains only calendar years AD) was extended by Bede to the complete Christian era (which contains in addition all calendar years BC but no year zero). Ten centuries after Bede the French astronomers Philippe de la Hire (in the year 1702) en Jacques Cassini (in the year 1740), purely in order to simplify certain calculations, put the Julian Dating System (proposed in the year 1583 by Joseph Scaliger) and with it an astronomical era into use which contains a leap year zero, which the year 1 (AD) precedes but does not exactly coincide with the year 1 BC. Astronomers never proposed seriously to replace our era with their astronomical era (which for that matter coincides exactly with the Christian era where it concerns the calendar years after the year 4).

Other familiar chronological subjects are for example: timeline, linear timescale, French revolutionary era, leap year, Hebrew calendar. Subjects of the Christian chronology are for example: Dionysius Exiguus' Easter table, Paschal full moon, lunar cycle, solar cycle, easter cycle, lunar phase number, millennium question.

In the absence of written history, with its chronicles and king lists, late 19th century archaeologists found that they could develop relative chronologies based on pottery techniques and styles. In the field of Egyptology, William Flinders Petrie pioneered sequence dating to penetrate pre-dynastic Neolithic times, using groups of contemporary artefacts deposited together at a single time in graves and working backwards methodically from the earliest historical phases of Egypt. Compare the American technique of Seriation.

Known wares discovered at strata in sometimes quite distant sites, the product of trade, helped extend the network of chronologies. Some cultures have retained the name applied to them in reference to characteristic forms, for lack of an idea of what they called themselves: "The Beaker People" in northern Europe during the 3rd millennium BCE, for example. The study of the means of placing pottery and other cultural artifacts into some kind of order proceeds in two phases, classification and typology: Classification creates categories for the purposes of description, and typology seeks to identify and analyse changes that allow artifacts to be placed into sequences [1].

Laboratory techniques developed particularly after mid-20th century helped constantly revise and refine the chronologies developed for specific cultural areas. Unrelated dating methods help reinforce a chronology, an axiom of corroborative evidence. Ideally, archaeological materials used for dating a site should complement each other and provide a means of cross-checking. Conclusions drawn from just one unsupported technique are usually regarded as unreliable.

Bayesian analysis has recently started to be routinely applied in the analysis of chronological information, including radiocarbon-derived dates,

Several legendary sources tend to assign unrealistically long lifespans to pre-historical heroes and monarchs (e.g Egypt, Hebrews, Japanese), if the number of years there reported are understood as years of more than 340 days. One potent explanation for this has been that there have been more than one harvest during the actual year, and memories evolving to legends tend to count each growth period as separate year.

Though chronologies formulated before the 1960s are subject to serious skepticism today, more recent results are more robust than readily appears to journalists and enthusiastic amateurs.

• See the list of timelines for Wikipedia chronologies.
• WikiTimeScale, interactive wiki with graphically displayed chronology of historic events

• Dendrochronology counts growth rings in timber, and correlates patterns
• Magnetosphere chronology
• Radiocarbon dating
• Thermoluminescence measures when objects were last heated
• Glottochronology dates events related to language evolution

• Order (sort)
• New Chronology
• Reverse chronology
• Synchronoptic view

• M. Aitken, Science-Based dating in Archaeology (Thames and Hudson, London) 1990: a recent overview

• Christian Chronology
• Regnal Chronologies
• A Timeline of Timelines
• A historical animated timeline creation tool
• Timeline of Evolution, Culture and Knowledge
• Timelines of History, Today in History, World History
• Timelines.info Graphical timelines of world history
• WikiTimeScale, Wiki for graphical illustration of historic events, persons and so on.
• Historical Timelines
• Dating Methods: an introduction (broken on 18-09-2007)
• Dating the Past
• Pragmatic Bayesians: a decade of integrating radiocarbon dates in chronological models (broken on 18-09-2007)