Technical Chronology
by Lance Latham

  1. Definition
  2. History
  3. Technical reasons for decline
  4. Current status
  5. The burgeoning problem
  6. The solution

1. Definition

Chronology is defined as "the science of computing time or periods of time, and of assigning events to their true dates" [1]. It should be distinguished from "chronometry", defined as "the art or science of accurately measuring time" [1].

Several points about these definitions should be emphasized. First, chronology is a science. Second, it is a computational science. Third, it is concerned with computing time, not measuring it. Fourth, there are essentially two parts to the definition of chronology. The first part defines a science of computation, while the second concerns the matter of "assigning events to their true dates". The second part may be distinguished from the first as a more historical and often narrative approach to the material. Thus, one may distinguish "technical" chronology as consisting of the first part of the definition, which concerns the computation of time, as opposed to "historical" chronology.

The Library of Congress selected the term "technical chronology" for its subclass "CE", which primarily concerns calendars. While the LC classification scheme is a dated and static system, a happy coincidence of definition in this instance buttresses the case for the use of the term "technical chronology".

Chronology is therefore well defined in dictionaries, and is recognized as a legitimate subject by at least one major classification scheme, so there can be no serious quibble about its existence as a field of study.

2. History

Chronology was certainly considered to be a legitimate field of study through the medieval, Renaissance and Baroque periods. Many "ecclesiastical histories" are chronologies in the second sense of narrative accounts. Biblical chronology has been a pit for absorbing intellectual energy for centuries. The subject has, over the course of many years, attracted some of the finest minds around the globe.

Joseph ScaligerJoseph Justus Scaliger (1540-1609) was considered to be the foremost scholar in sixteenth-century Europe, referred to as "the light of the world", "the sea of sciences" and similar epithets [2], and it is to him that we owe a "modern" definition of chronology, with the publication of "De Emendatione Temporum" in 1583 and the "Thesaurus Temporum" in 1606. His work, and the work of a number of imitators, like the Jesuit Dionysius Petavius (1583-1652), essentially defined the "official" chronology of world events for centuries to come. The real importance of Scaliger's work to chronology, however, resides not so much in his results but in the quality of his work, his introduction of new methods such as the Julian Period and his insistence upon a rigorous criticism of sources, and his redefinition of chronology itself. Chronologers before Scaliger viewed the field from a religious perspective, seeking a moral order in the past. Chronology was "pedagogical in intent and elementary in execution", as Grafton [3] would have it.

No less a figure than Isaac Newton (1642-1727) also took an active interest in the field, publishing "The Chronology of Ancient Kingdoms Amended", a substantial monograph disputing several key conclusions in Scaliger's work. Scaliger's conclusions were also disputed by several of his contemporaries, including Arcilla, a professor at Salamanca University, and Hardouin, director of the French Royal Library, among many others.

The work of Scaliger and his imitators of the seventeenth century, however, represents a high-water mark for the field of chronology for several centuries thereafter. The reasons are varied and instructive.

First among these reasons must be the general intellectual climate of Europe in the sixteenth and seventeenth centuries. This period marked the beginnings of the modern age, particularly with regard to a willingness to question Biblical authority. There were limits to how far the scholars of the day were willing to go in that matter, however. Scaliger discredited the forgeries of Annius of Viterbo, for example, upon which many chronologers had depended wholly or in part, and insisted upon the independent value of pagan, non-Biblical sources. But he viewed the Bible as the only completely reliable source, as did virtually every one of his contemporaries.

As Grafton [3] notes of the later chronologers in the eighteenth century, "All of them were writing chronology not in order to recover an unknown past but in order to prove points in polemics that lay outside the field of chronology — for the most part, points in theology or in the comparative history of religion." The consequences of this mind-set were predictable. Grafton [3] continues, noting "And as the motives of chronological writers came once again to resemble the unscholarly motives that had been prevalent before Scaliger, so too their methods returned to the arbitrary and elementary state which Scaliger had reformed."

In part, Scaliger himself perhaps sowed the seeds of later decline. He had uncovered material that challenged the religious perspective of his contemporaries, but was unable to provide critical tools for resolving the resulting intellectual conflict. The idea of scientific inquiry had certainly been born, but it had by no means triumphed. The challenge of new ideas led many to desperately seek and impose a new sense of order in this period, and scholars were no exception. The resulting application of ideology to scholarship led inevitably to a general decline in quality.

A related intellectual trend of the time was the new prestige of philosophy and the exact sciences. Chronology was viewed as an antiquarian disciplines, and tended to attract only pedantic compilers and gifted amateurs. The irresolvable arguments in which the field became mired only tended to hasten the general process of decline.

3. Technical reasons for decline

Turning to more technical reasons for the general decline of chronology by 1700, it is apparent that Scaliger and his imitators had largely exhausted the available technology of their day. Scaliger was a brilliant scholar who studied mathematics among his many accomplishments, but he was not a mathematician. His geometrical proof of the quadrature of the circle is false, for example, although he defended it during his entire lifetime. As a consequence, Scaliger set chronology on a general course that did not emphasize mathematics, although it certainly used mathematics productively.

Historically, however, additional substantial progress in chronology simply had to wait for two developments:

(a) an external means of validating chronology (archaeology and dating techniques)

(b) some means of performing extended mathematical computations that permit exploring complex scenarios and relationships in a reasonable time frame (computers and their software).

In Scaliger's time, chronology focused of necessity on documents and epigraphical studies. No mature science of archaeology existed in his day, and no scientific techniques for dating objects and documents were available. As a consequence, no field external to chronology existed that could validate or invalidate, corroborate or disprove, any conclusions reached by a chronologer.

Likewise, neither Scaliger, nor his imitators or contemporaries had readily available computation resources that would have enabled them, for example, to compare dates with astronomical events with speed and accuracy, correlate complex chronologies, or perform any of the other involved computations that form a necessary part of the modern research arsenal.

That chronology languished as a field of study for several centuries is not an unusual occurrence in the history of science. Science often progresses at an uneven rate, waiting for technological breakthroughs or progress in related fields to spark innovation or permit further evolution. Chronology is a science. Lacking an external means of validation, and links to other related sciences, it could not free itself from potential capture by polemicists and ideologues. Chronology is also, by definition, a computational science. Without computational resources, it could not proceed past manual mathematics.

4. Current status

Historically, the two impediments to the progress of chronology were largely removed by the mid-twentieth century. Archaeology had advanced as a science and was joined by techniques such as radio carbon dating and dendrochronology that permitted external validation of the findings of chronology. The entire question of the dynastic chronology of Egypt, for example, over which Scaliger and later chronologers famously stumbled, only began to achieve a tenuous consensus in the twentieth century [6], owing to new archaeological discoveries and new dating methods.

In the area of compuation, Hawkins [4] published innovative work demonstrating the application of computer software and statistical analysis to Stonehenge in 1965, and Goldstine [5] published computer-generated Babylonian menologies in 1973. Fliegel and van Flandern introduced the notion of algorithms for performing conversions between calendar dates and Julian Day numbers in 1968 [7].

The removal of the long-standing impediments to progress did not, understandably, instantly remove the effects of a delay of some three centuries duration. Scholars interested in chronology as a discipline still find that they are obliged to study and publish in many other established fields, as varied as astronomy, medieval history, mathematics, philosophy, Egyptology, and the history of science. The literature of chronology, while quite large, is therefore badly scattered and is not regarded as a coherent body of knowledge.

Another consequence of the delayed development of the field is the fact that chronology is simply not currently regarded as an academic discipline, despite its current importance and lengthy history. No university, to this author's knowledge, offers a degree in chronology. No national or international body of chronologers exists, and no major journal is dedicated to chronology. As a further consequence, few scholars have any formal training in chronology, leading to a situation in which literature and products requiring knowledge of chronology are often badly flawed or limited. All of these situations are simply symptoms of a single cause, which is the fact that chronology is not currently recognized as a field of study.

5. The burgeoning problem

If chronological concerns were merely the province of a handful of scholars or calendar buffs, and lacked any wider application, one might be forgiven for dismissing chronology as largely irrelevant to the modern world.

Such is not the case.

In the past several decades, computer resources have become almost ubiquitous. Not surprisingly, the software that runs on those computers is generally concerned with solving problems that humans believe to be important, such as payroll, accounting, scheduling, etc. Since all human activity occurs in the context of time, it is not surprising that a lot of that software concerns dates and times.

In fact, a 1996 survey of corporate customers by Viasoft, Inc. looked at software by industry type and found that an average of 89.35% of all programs were affected by the Y2K bug. Depending upon the source and date of the estimate, the global cost of the Y2K bug was between 600 billion and one trillion dollars. By any rational measure, that level of expenditure qualifies as a serious and practical concern.

The Y2K bug was simply one instance of one class of problem with chronology software. There are many other known instances of the problem class, known as "date rollover", and other classes of problem [8]. As a class, in fact, chronology software probably affects more programs than any other, and as a consequence of its ubiquitous nature, it is more expensive to modify than any other.

Since chronology is a computational science, and since computation is now almost exclusively the preserve of computer software, chronology has therefore become very largely a matter of computer software.

Owing to the situation described in the last section, however, chronology software is often ill conceived, poorly designed, and badly implemented. Lacking formal training in chronology, most developers do not understand the basic issues. The general result has been a hodge-podge of ad hoc solutions to individual problems, and an almost complete lack of a unifying view of the field, coupled with a virtually complete absence of tools and methodology. Two attempts to define systematic approaches to chronology algorithms and data structures were published independently within a few months of each other in 1997 [9] and 1998 [10].

The failure to comprehend the actual current role and importance of chronology software in the modern world, especially as humans rely increasingly upon computers for mission-critical applications in which human lives are at risk, is simply no longer an affordable luxury. Not only are hundreds of billions of dollars at stake, but the increasing reliance of society on computers means that any systematic software problem that prevents proper operation of a large percentage of its computers presents a very real risk of causing the collapse of the entire economic system.

6. The solution

The existence of computer software has revitalized and redefined the field of technical chronology. It has become a vital concern, however, that chronology software be well designed and implemented. In order for developers to understand the role of chronology software in their systems, it is essential that they be able to receive proper training in that field.

Therefore, the inescapable conclusion must be that chronology must re-assert itself as a coherent and defined field of study. The time for doing so is appropriate, now that the necessary tools and interest in the field are in place.

The first step in this process is the creation of a refereed journal, dedicated specifically to chronology. The next step is the sponsorship of conferences and the generation of interest in chronology as a discipline at the university level. Next, the formation of a committee to produce a body of knowledge, along the lines of SWEBOK (the Software Engineering Body of Knowledge), is essential to define the structure of the discipline and its literature.

The next essential step is the definition of introductory courses at the university level, and the incorporation of the field into university curricula and plans of study. This should begin at the graduate level, so that graduate students can study the area and acquire expertise, and more immediately begin to apply that knowledge in their work.

If it is to survive in the modern world, chronology must establish its relevance to modern society, and if it is to thrive in the academic world, it must be able to attract students and grant money from corporate sponsors and government. The chance to define a "new" field should attract students with initiative and ambition. Funding for grants will come when workers in the field find methods for making the easily supported case that chronology software has great economic importance.


1. Onions, C.T. (ed.), 1969, "The Shorter Oxford English Dictionary", 3rd ed., Clarendon Press, Oxford.
2. Smith, P., 1962, "Origins of Modern Culture: 1543-1687", Collier Books, New York.
3. Grafton, A.T., 1975, "Joseph Scaliger and Historical Chronology: The Rise and Fall of a Discipline", History and Theory, v14, 156-185.
4. Hawkins, G.S., 1965, "Stonehenge Decoded", Doubleday & Co., Garden City, NY.
5. Goldstine, H., 1973, "New and Full Moons 1001 B.C. to A.D. 1651", American Philosophical Society, Philadelphia.
6. Gardiner, A. 1961, "Egypt of the Pharoahs: An Introduction", Oxford.
7. Fliegel, H.F. and van Flandern, T.C., 1968, "A machine algorithm for processing calendar dates", CACM, v 11, n 10, 657.
8. Glass, R.L., 1997, "The next date crisis and the ones after that", CACM, v 40, n 1, 15-17.
9. Dershowitz, N. and Reingold, E., 1997, "Calendrical Calculations", Cambridge University Press, Cambridge.
10. Latham, L., 1998, "Standard C Date/Time Library", R&D Books, Lawrence, KS.

Copyright 2004 Lance Latham

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