Accepted systems for the division of time into days, months, and years, calendars reflect a human effort to measure and order extended periods of the future. Scholars divide calendars into three general categories—lunar, solar, and lunisolar—depending upon whether their temporal divisions are principally based upon the movements of the moon or the sun or on a compromise between both. Regarding Western forms of chronology, in which solar reckoning of time predominates, historians have studied calendar reform, which encapsulates many scientific advancements and cosmological debates of the Renaissance and Enlightenment. In their studies of other parts of the world, where lunar calendars tend to prevail, commentators have tended to seek a comparative understanding of the various means of envisioning and organizing time across the globe and the cultural implications of such systems.Used to regulate civil and religious observances, as well as agricultural and business affairs, calendars offer valuable insights into the historical development of cultural and scientific standards within a society.
Historically, the creation of a calendar that provides both a satisfactory representation of time and practical value for the ordering of life has proved a vexing problem. Technical difficulties associated with measuring time on Earth and ignorance of the true structure of the solar system proved the greatest impediments to accurate measurement. Such problems began with the length of the day, the basic division of calendrical time. Early astronomers computed the amount of time required for the Earth to complete one rotation about its axis in relation to either the Sun—the solar day—or another, more distant star—the sidereal day. Because of practical variations in the computed values, however, astronomers found it necessary to use an average value, the mean solar day, for use in devising a calendar. The next important calendrical division, the month, was commonly associated with the orbit of the moon around the Earth. Ancient observers recorded months based upon the cycling of the moon through its phases, from full to new and full again—a process that occurs approximately every 29 and one half days and is called the synodic month. Early calendar-makers then divided time into years by examining the period required for the Earth to complete one full orbit around the sun. Several means of determining this value have been applied since antiquity, but among the most useful has been the measurement of the tropical year. Determining the length of the tropical year involves calculating the period of time elapsed between the sun's passage through successive vernal equinoxes—moments marking the beginning of Spring when the sun is directly above the equator and the hours of day and night are equal. Prior to the twentieth century, such calculations produced inaccuracies on the scale of several minutes. Due to such errors, and because the values used in dividing time according to lunar or solar reckoning produced such widely divergent results, calendar-makers found it necessary to introduce intercalations to the calendar year, adding days where appropriate in order to maintain consistency between the accepted values for the length of a month and the actual time required for the Earth to complete its transit around the sun.
The origins of the calendar in the West can be traced to the astronomical reckoning of the ancient Egyptians, who devised a system based upon a year of 360 days with an additional five-day intercalation. Later, the Greek astronomer Eudoxes amended this calendar, calculating the year at 365 days and six hours, which more closely approximates the true value of the tropical year. This system was then adopted by the Romans in 45 bc to replace their flawed calendar. Forwarded by Julius Caesar under the advisement of the astronomer Sosigenes, the Julian Reform called for an abandonment of lunation and for reliance on a completely solar calendar. The system instituted the leap year, adding one day to the calendar every four years, but even with the leap year fix it was unsatisfactory—the Julian year was still 11 minutes and 14 seconds longer than the tropical year. The resulting discrepancy produced significant conflicts between calendar dates and the observable seasons over the course of the ensuing centuries. Nevertheless, the new system proved vastly superior to its predecessor. It was accepted throughout the Roman world, and in 325 ad made the official doctrine of Christendom by the first Council of Nicea.
By the late sixteenth century, advances in astronomy had radically pushed the possibility of calendar reform ahead. The real impetus for updating the calendar, however, came from a need to establish the correct time for the celebration of Easter. In 1582 Pope Gregory XIII issued a papal bull instituting a reform of the Julian calendar in which several days were dropped to reset a system that had strayed dramatically. Building upon the work of the astronomer Christoph Clavius, whose calculations had produced a closer approximation of the tropical year, the Gregorian Reform removed centurial leap years, except for those divisible by 400. While the reform was rapidly accepted throughout Catholic Europe, Protestant countries were resistant. Over time, new scientific discoveries concerning the mechanics of the universe were brought to light, causing astronomers, regardless of religious persuasion, to acknowledge the errors of the old system. Notably, as the work of Sir Isaac Newton in the seventeenth century effectively annihilated the last remnants of the ancient and flawed Ptolemaic cosmological model and presented a new vision of the universe, resistance began to erode. Eventually the German states fell into line by 1699, in large part due to the lobbying efforts of Newton's contemporary, Gottfried Wilhelm Leibniz. Still, the change was not accepted until 1752 in England, where, tradition has it, the loss of 11 days in the calendar sparked protest—the so-called British time riots—throughout the county.
The Gregorian calendar, while much more accurate than its Julian predecessor, was still not completely in accordance with empirical reality. And while considerable advancements have since been made in the measurement of time, astronomical variables—such as changes in the motion of the Earth and the sun, and the inevitable, if slight, drift of the equinoxes—make the proposition of a perfectly accurate calendar an unattainable one. Meanwhile, scholars continue to study developments in the calendar over the centuries, and the cultural importance of these changes. Additionally, a variety of non-western calendars employed around the world—such as the lunisolar Jewish calendar, and the lunar-based Chinese and Islamic calendars—have attracted the interest of cultural critics. Other scholars continue to examine historical calendars, such as the elaborate lunar system employed by the pre-columbian Mayan civilization of Central America, for insights into astronomical influence on the construction of society.
L'Art de verifier les dates 8 vols. (treatise) 1783
Kalendarium Gregorianum perpetuum cum privilegio summi Pontificis et aliorum Principum (essay) 1582
Astronomy explained upon Sir Isaac Newton's Principles (treatise) 1770
La Chiave del Calendaro (treatise) 1583
The Chronology of Ancient Kingdoms Amended (treatise) 1728
De Doctrina Temporum (treatise) 1627
The Calendar, Its History, Structure and Improvement (nonfiction) 1921
De Emendatione Temporum (treatise) 1634
Alexander Philip (essay date 1921)
SOURCE: “Part I,” in The Calendar: Its History, Structure and Improvement, Cambridge University Press, 1921, pp. 1-27.
[In the following excerpt, Philip surveys the historical measurement of time, reviews the development and reform of the Western calendar, and looks at several world calendars.]
THE MEASUREMENT OF TIME
Our knowledge of time is wholly dependent on measurement. Without the specification of magnitude or quantity the idea of time is meaningless. Now, we can measure time—physically—in one way only—by counting repeated motions. Apart, therefore, from physical pulsations we should have no natural...
(The entire section is 9080 words.)
E. G. Richards (essay date 1998)
SOURCE: “The Variety of Calendars,” in Mapping Time: The Calendar and Its History, Oxford University Press, 1998, pp. 89-109.
[In the following excerpt, Richards summarizes the types, characteristics, and sources of various calendars.]
Men have ordered their affairs by the phases of the moon and the seasons for as long as records exist. Even before calendars had been invented they could have told their wives that they would be back three days after the next full moon or remarked that their son was born three winters ago. Such perhaps were the beginnings of calendars. Later, men counted the days between moons and...
(The entire section is 7257 words.)
Criticism: Measuring Time
Meredith N. Stiles (essay date 1933)
SOURCE: “The Persistence of a Relic” and “Astronomical Facts and Human Failings,” in The World's Work and the Calendar, Richard G. Badger, 1933, pp. 11-16, 22-32.
[In the following excerpt, Stiles explores the difficulty of measuring time and the origins of the calendar.]
THE PERSISTENCE OF A RELIC
Does it not seem strange that whereas our civilization has established fixed systems for computing the three dimensions of Space and the force of Gravity, it has failed to provide for ordinary use a fixed system for computing Time? Why has the application of good sense to Time measurement been neglected in the progress of human affairs?...
(The entire section is 4146 words.)
Arno Borst (essay date 1993)
SOURCE: “The Universal Machine and Chronology in the Early Modern Period,” in The Ordering of Time: From the Ancient Computus to the Modern Computer, translated by Andrew Winnard, University of Chicago Press, 1993, pp. 101-12.
[In the following essay, Borst highlights the relationship between calendar-making and advancements in computational mathematics in the sixteenth century.]
The age of perfection began with Canon Nicholas Copernicus. In 1543 he reminded Pope Paul III of the last Lateran Council and his questio de emendando kalendario ecclesiastico. In doing so, he justified his ‘more precise computation of times [supputatio temporum], required...
(The entire section is 3926 words.)
Criticism: Calendars And Culture
François Laroque (essay date 1975)
SOURCE: “A Comparative Calendar of Folk Customs and Festivities in Elizabethan England,” in Cahiers Elisabéthains, No. 8, October, 1975, pp. 5-13.
[In the following essay, Laroque investigates the origins and representation of folk festivals in the Elizabethan calendar.]
As E. K. Chambers says in The Medieval Stage,1 the student of English popular ludi and fêtes cannot but be put off by the complexity and confusion of the recorded material. We are very much in need of a clear and systematic calendar establishing the precise place and function of all these traditional ceremonies, in order to complete the study of their local and...
(The entire section is 2357 words.)
David Cressy (essay date 1989)
SOURCE: “The English Calendar in Colonial America,” in Bonfires and Bells: National Memory and the Protestant Calendar in Elizabethan and Stuart England, Wiedenfeld and Nicolson, 1989, pp. 190-206.
[In the following essay, Cressy evaluates changes in the Protestant English calendar occasioned by its transfer to the New World.]
The English calendar amalgamated astronomical, classical-pagan, and traditional Christian elements. In addition to marking the seasons and pacing the agricultural year, the calendar fixed and proclaimed the major Christian holy days, and registered such secular events as law terms, court days, times of fairs, and anniversaries. Lady day, May...
(The entire section is 8450 words.)
Bridget Ann Henisch (essay date 1995)
SOURCE: “In Due Season: Farm Work in the Medieval Calendar Tradition,” in Agriculture in the Middle Ages: Technology, Practice, and Representation, edited by Del Sweeney, University of Pennsylvania Press, 1995, pp. 309-36.
[In the following essay, Henisch studies the visual depiction of agricultural labor in the calendars of the Middle Ages.]
When a medieval artist was told to illustrate a calendar, he knew exactly what he was expected to provide. It made no difference whether he was working in wood or in stone, tracing the design for a stained-glass window, or brushing gold onto a sheet of vellum. He reached into his store of patterns and pulled out, not twelve...
(The entire section is 6623 words.)
Francois B. Brévart (essay date 1996)
SOURCE: “Chronology and Cosmology: A German Volkskalendar of the Fifteenth Century,” in Princeton University Library Chronicle, Vol. LVII, No. 2, Winter, 1996, pp. 224-65.
[In the following excerpt, Brévart analyzes fifteenth century manuscripts of a Volkskalendar—a collection of astronomical, seasonal, and biographical data.]
In 1946, the Princeton University Library acquired a group of fifty-eight Western European medieval and Renaissance manuscripts from the Grenville Kane Collection.1 Among them was a bound manuscript written in German and consisting of twenty-one parchment leaves measuring 19 x 14 centimeters, with approximately...
(The entire section is 10869 words.)
Criticism: Calendar Reform
Paul Alkon (essay date 1982)
SOURCE: “Changing the Calendar,” in Eighteenth Century Life, Vol. VII, No. 2, January, 1982, pp. 1-18.
[In the following essay, Alkon comments on eighteenth-century attitudes toward time and changes in the calendar.]
In January 1796, Neville Maskelyne, astronomer royal at Greenwich, fired his assistant, Kinnebrook, charging him with an observational error of eight-tenths of a second. Kinnebrook's difficulty had started the previous August when his notations of stellar transit times began to differ by one-half second from those of Maskelyne, whose admonitions were to no avail, and whose patience was exhausted four months later upon seeing the discrepancy grow by...
(The entire section is 9057 words.)
H. M. Nobis (essay date 1983)
SOURCE: “The Reaction of Astronomers to the Gregorian Calendar,” in Gregorian Reform of the Calendar, edited by G. V. Coyne, M. A. Hoskin, and O. Pedersen, Pontificia Academia Scientiarvm: Specola Vaticana, 1983, pp. 243-54.
[In the following essay, Nobis details criticism of the Gregorian calendar reform by contemporary scientists.]
This paper has a bearing not only on the history of chronology in particular, but on the history of science in general. The reaction of astronomers to the calendar reform provides us with a very good example of the general problems involved in such an undertaking, especially those deriving from the practical needs of society....
(The entire section is 4635 words.)
David Ewing Duncan (essay date 1988)
SOURCE: “Solving the Riddle of Time,” in Calendar: Humanity's Epic Struggle to Determine a True and Accurate Year, Avon Books, Inc., 1998, pp. 187-208.
[In the following essay, Duncan recounts the efforts of those involved in the Gregorian calendar reform, the technical difficulties they faced, and the reaction to their work.]
The patriarch has also subscribed to our calendar and admitted that it is very good. I hope that it will soon be published, because the Pope is quite eager.
—Christopher Clavius, 1581
None of the three men responsible for fixing the calendar was a conqueror, notorious...
(The entire section is 7946 words.)
Robert Poole (essay date 1998)
SOURCE: “The Problem of the Calendar,” in Time's Alteration: Calendar Reform in Early Modern England, UCL Press, 1998, pp. 31-44.
[In the following excerpt, Poole examines the Julian calendar, its Gregorian reform, and the gradual acceptance of the reformed calendar in Protestant Europe.]
Easter is a feast, not a planet. You do not determine it to hours, minutes and seconds.
Since the start of the Christian era, the calendar has been one of the most fertile of all sources of theological controversy.1 The calendar was never merely a system of calibrating the year, capable of...
(The entire section is 7333 words.)
Black, F. A. The Calendar and Its Reform. London: Gall and Inglis, 1932, 80 p.
Details the Julian and Gregorian reforms of the Roman calendar.
Landes, David S. Revolution in Time: Clocks and the Making of the Modern World. Cambridge, Mass.: Harvard University Press, 1983, 482 p.
In-depth history of one thousand years of innovation in time measurement.
Mukherjee, Sudhish Kumar. Calendar: An Analytical Investigation. Calcutta: Progressive Publishers, 1978, 32 p.
Comparative study of the Gregorian and Indian calendars.
O'Neil, William M. Time and the Calendars....
(The entire section is 371 words.)