The term chronology is derived from Greek XpovoXoyia, or computation of . In contempo­rary science, chronology is understood simultane­ously as a consequence of historical events in and as a discipline dealing with regularities of these events as arrangements in , as well as with gen­eral principles and scientific methods of mea­surement. In this context, chronology could be viewed in at least three main dimensions: astro­nomic, historical, and general chronology.

Astronomic Chronology

Astronomic chronology is a branch of chronology that studies regularities of repeated celestial phe­nomena, establishes precise astronomic time, and often is understood as one of the basic methods of historical chronology. In this dimension it is very close to timekeeping, or chronometry.

Small-scale observations of astronomic chronol­ogy are based on the earth’s spinning motion (the so-called sidereal day) and the earth’s revolution around the sun (true solar day), while longer periods usually involve observations of the visual localization of the moon and sun among stars of the celestial sphere (sidereal and synodic month, sidereal and tropic year). On this basis, different systems of solar, lunar, and lunisolar calendars were developed, and their earliest forms can be traced back to late prehis­toric times. The history of the invention and imple­mentation of different forms of timekeeping are the subject of the other branch of chronology— historical or technical chronology.

Historical (or Technical) Chronology

This type of chronology traditionally is regarded as a special subdiscipline of history, occupied with the study of calendars and calendar systems as these existed in the historical past in different regions of the world. Among the important tasks of this branch of chronology are the assignment of precise dates to events and phenomena, defining the time of historical narratives (chronicles), and specification on this basis of the true dates of par­ticular facts. In such a context, historical chronol­ogy is deeply connected with other historical subdisciplines—historiography and the study of historical sources.

Studies of Calendars and Calendar Systems

The alteration of day to night was already obvi­ous to early prehistoric hunter-gatherers and prob­ably was reflected in the peculiar Magdalenian notched bones that are often regarded as the earliest archaeological records of primitive notational sys­tems. The origin of land cultivation and agriculture required more complicated chronometry where warm/cold and dry/wet seasons’ alternation and repeated climatic events such as inundations were taken into consideration. Such observations could be recorded in the ornamentation of special forms of ceramic vessels and clay figurines used in celebra­tion of fertility rites and traditional ceremonies sup­posed to exert an influence over the weather. Most such systems were correlated with the vernal and autumnal equinoxes, which were marked by special ceremonies involving thousands of people. Probably the original megalithic constructions, such as Stonehenge in Britain, were specially built to make these events easy to observe for shamans and pagan priests and illustrative for local populations. According to oral tradition, Druid priests were highly skilled in the organization of such calendar ceremonies.

The first complex calendar systems based on obser­vation of lunar and solar phases appeared during the period of the formation of early civilizations in the Near East and were connected with the necessity of rational organization of the early state economy as well as appropriate celebration of basic cults of the community. Traditionally, it is thought that the earli­est forms of the were invented in ancient Egypt, and, with slight modifications caused by the need to correlate the with the true astronomic year, reflected in the introduction of the leap year, it remains widely used in contemporary Western civilization. Early forms of the were developed by the Arabs, and today this calendar remains the basic form of timekeeping in the Muslim world. The ancient Hebrews are regarded as inventors of the , which continues to be applied in traditional Jewish chronometry up to the present day. Other ancient civilizations created their own particular systems of timekeeping, among which are included the Babylonian, Persian, Chinese, Indian, and Vietnamese calendars.

Rapid development of mathematics and astron­omy in ancient Greece contributed greatly to the comprehension of discrepancies between the rough division of time into years and the real recurrence of celestial events. In order to correlate the solar calendar with astronomic reality, an 8-year system based on the addition of a supplementary month every 3rd, 5th, and 8th year of the cycle and the so-called Methon cycle was introduced.

The Roman calendar in its early stage was less than precise, consisting of only 10 solar months. Its principal revision, undertaken in 46 BCE under the initiative of Julius Caesar on the basis of advice from Sozigen (an astronomer from Egyptian Alexandria), resulted in the expanded Julian calen­dar, the basic cycle of which consists of 3 years of 365 days each and 1 leap year of 366 days. This calendar, introduced on January 1, 45 BCE, and in regular use since the 8th year of the common era, was the basic frame of timekeeping in Europe and its colonies until the end of the 16th century.

The reason for a new revision of the calendar was a discrepancy between the astronomic and the calendar vernal equinox, which was noticed for the first time at the end of the 13th century and became more and more apparent during subse­quent ages. Pope Gregory XIII, by his decree of February 24, 1582, introduced amendments to the . His new version was called the . It was immediately applied in the Catholic countries, while most of the Protestant nations adopted it only in the 18th century. The transition of the civil states of Russia, Bulgaria, Serbia, Romania, and Greece (countries with pre­dominantly Orthodox Christian populations) to the at the beginning of the 20th century made it the most widespread form of timekeeping in the world. Nevertheless, the Orthodox Church officially rejects the and still maintains its own system of timekeeping, based on the , to the present day.

Apart from these widely disseminated and well- studied calendar systems in the historical past, many other forms of systematic timekeeping based on solar, lunar, and combined lunisolar time observations were used. Some of them still remain in use, mostly in vast areas of Eastern Asia (in the traditional Chinese and Japanese calendars) and in Muslim communities all over the world that observe the traditional ; others are used only in the context of traditional rituals and ceremonies of native cultures (e.g., calendars of the ancient Maya) or have become an integral part of Western civilization’s spiritual life (e.g., the zodiacal calendar). Calendars have also been introduced in the wake of -making events in modern times (e.g., the calendar of the French Republic, and the Soviet revolutionary calendar); these soon became obsolete. In the contemporary world community, the Gregorian system of time­keeping is recognized internationally by official bodies; the other calendars can be applied locally, ethnically, or occasionally.

Historical Events and Phenomena Dating

Specification of the true dates of historical events is another important task of historical chronology. This procedure is based on two kinds of primary data: one originated from historical sources (chronicles, narratives, etc.) and the other obtained with the help of natural sciences.

In the case of historical sources, determining their true dates, authenticity, and reliability is a cornerstone of the dating process. In most cases, the problem of historical source verification is solved through multilevel comparisons of different sources and their correlation with data from the natural sciences, if available.

Usually a distinction is made between absolute and relative dating. Relative dating is aimed at defining the strict order of certain events or delineating the period of time when they could have happened. Relative dating is most widely applied in archaeology, based on typological and stratigraphic methods. Relative dating is impor­tant in many social sciences when determining the actual date of an event or phenomenon is not pos­sible. In these cases, cross-dating based on match­ing known dates for events and phenomena can be used. Glottochronology, which attempts to deter­mine when certain languages separated based on the percentage of words remaining from their pri­mary basic vocabularies, is another example of relative dating methods.

The goal of absolute dating is to identify actual dates of specific events. In history this is usually expressed as a day, month, year, or century; in archaeology it might be in thousands or even millions of years. Absolute dates are established with the help of the scientific methods of the natural sciences or by correlation with established actual dates of other events.

Physical methods of absolute dating have been considered to be most reliable since radio­carbon dating was invented in 1946 and rapidly introduced into scientific methodology all over the world. This method is currently widely used for the dating of organic artifacts (objects made mostly of bone and wood). Later, thermolumi­nescence and uranium-thorium balance dating methods were added to absolute dating methods and helped to cover intervals of up to several million years. Chemical methods of absolute dating, such as the obsidian hydration technique, are also used to determine ages of relatively “old” objects as precisely as possible. Biological dating, such as dendrochronology, which dates objects based on the annual growth rings of trees, is used to examine artifacts like buildings. It is useful for relatively “young” artifacts that are no older than several centuries.

When it became possible to derive absolute dates by comparing a variety of sources, the problem of correlating, for example, references referring to “years ago” versus “years before Christ” became especially critical. During the past decade this problem was often considered more serious than deriving the correct date.

General (or Scientific) Chronology

The main task of general chronology is the reconstruction of the exact order of historical events and phenomena as well as establishing the duration of historical processes. General chronology (as well as dating) can be precise only when an event or phenomenon can be dated with absolute numbers, or relative if ascertaining the order of events or by determining a time period in which they could have taken place. Ancient chronologies, often referred to in most of the important events and phenomena in the histories of specific populations (nation, country, etc.), were regarded by their creators as the best way to satisfy the needs of both versions of general chronology.

In Ancient Egypt, events usually were dated con­secutively based on the year of a specific pharaoh’s rule. Every new pharaoh established his own “era” of timekeeping. A crucial task in Egyptian chronol­ogy is determining the details and specifics of each pharaoh’s rule.

Ancient Greek history offers a more complicated version of event correlation with the comparison of information about specific facts and events obtained from various historical narratives that were created in different periods. Even so, ancient Greece has no unified general chronology, and historians have to date an event simultaneously in several year-keep- ing systems, the most widespread of which are cor­related with the reigns of Persian rulers and the governments of Ephorus of Sparta and Archonts of Athens. In the 4th century BCE, historian Timaeus proposed introducing a general chronology based on lists of Olympiad winners, which had been kept since 776 BCE. This system was widely used by historians but not by official administrations. The first general scientific chronology of ancient Greece was created by Eratosthenes in the 3rd century BCE; he established the absolute date of several basic events (e.g., Xerxes’ invasion, the beginning of the Peloponnesian War, etc.) and on this basis calculated the dates of other events.

A general chronology of Roman history was based primarily on lists of Roman consuls, which are easily integrated with ancient Greek chrono­logical systems. Also, a dating system originating from the foundation of Rome (753 BCE) was introduced by Varro in the 1st century CE.

In the late Roman period, the Diocletian influ­ence became most widespread in 284 CE because of its connection with calculating the dates for Easter, but soon it was replaced by the “Christian era” introduced in 532 by Dionysius Minor as the ab incriptione era. During the Renaissance, his­torical event dating based on the Christian era developed into the modern chronology system, the basics of which were formulated by Joseph Scaliger (1540-1609). He managed to transfer all existing dates into a unique system of dating originating with the Julian period (started in 4713 BCE) and reintroduced the process of historical date verification by reference to astronomic events mentioned in historical sources. Later, Petavius proposed a system of back-keeping years before the Christian era; this scheme has been widely recognized since the 18th century.

Critique of General Chronology

The problem of the reliability and authenticity of dates is regarded as critical in both genres of general chronology, and it inevitably implies a process of exhaustive critique of various dates and their sources. So, for example, the Diocletian era was recognized as reliable when the starting date of Diocletian’s reign was established inde­pendently by three scientists using three different methods. This and a series of other coincidences established a background that allows scientists to believe that Roman general chronology is rather reliable. Greek chronology could easily be syn­chronized with Roman since there many dates known in both traditions. Synchronization of Egyptian, Persian, and some other chronologies widespread in the ancient Middle East is based on lists of rulers made by the Egyptian historian Manetho. Chinese general chronology also is regarded as rather reliable since even today it is based on the same 60-year cycles; in ancient times, moreover, it is reinforced by a highly developed historiographic tradition with a detailed chronology. The decree by India’s king Ashoka, in which names of Hellenistic rulers are men­tioned, is regarded as the cornerstone for verifica­tion of ancient Indian general chronology.

Another branch of general chronology cri- tique—the so-called New Chronology invented by the Russian academician Nikolay Fomenko in the late 1990s—makes the radical claim that all dates established in ancient times and studied today should be regarded as invalid. This con­cept is based on the assumption that all historical narratives in fact were created recently in attempts to prove the great antiquity of human history and culture, whereas the true duration of human history does not exceed a thousand years.

Fomenko’s hypothesis has provoked a new phase of discussion about the reliability and authenticity of general chronology that, it is hoped, will enable obtaining new details to enhance our knowledge of the human past.

Olena V. Smyntyna

See also Archaeology; Clocks, Biological; Dating Techniques; Egypt, Ancient; Geologic Timescale; Longevity; Rome, Ancient; Stonehenge; Time, Cosmic; Time, Historic; Time, Measurements of; Time, Perspectives of; Time, Prehistoric

Further Readings

Edwards, O. (1999). When was anno Domini?

Edinburgh, UK: Floris Books.

Harvey, O. L. (1983). Calendar conversions by way of number. Philadelphia: American Philosophical Society.

Higuera, T. P. (1998). Medieval calendars. London: Wiedenfeld & Nicolson.

van der Meer, P. (1947). The ancient chronology of Western Asia and Egypt. Leiden, The Netherlands: Brill.

Mellersh, H. E. L., & Williams, N. (1999). The Hutchinson chronology of world history. Oxford, UK: Helicon.

Poole, R. L. (1934). Studies in chronology and history. Oxford, UK: Clarendon Press.

Teeple, J. B. (2002). Timelines of world history. London: Dorling Kindersley.

Thomas, H. L. (1967). Near Eastern, Mediterranean and European chronology: The historical, archaeological, radiocarbon, pollenalytical and geochronological evidence. Lund, Sweden: Astron.

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