CALENDAR

any system for dividing time over extended periods, such as days, months, or years, and arranging such divisions in a definite order. A calendric system is essential for regulating the basic affairs of civil lifee.g., agricultural, business, and domesticand for reckoning time for religious observances and scientific purposes. There are several standard units common to virtually all calendric systems. The day is the fundamental unit of computation in any calendar. It is to some extent a natural division of time, since it is based on the length of time it takes the Earth to rotate once on its axis, but its subdivision into a number of equal intervals of, for example, 24 hours is purely artificial. The week, too, is an artificial division of time and cannot be correlated with any astronomical or natural phenomena except insofar as it is a closed cycle of days. The seven-day week that is now universally used may have been derived from the mystical significance attached to the number seven. Support for this view may perhaps be derived from the use of the names of gods and goddesses for each of the days (see week). The month is a calendric period derived from lunation, the time interval in which the Moon completes a full cycle of its phases. This period, known as the synodic month, consists of 29.53059 days. As the earliest adopted of the longer calendar periods, it had a significance in ancient religious observance. The year is based on the length of time it takes the Earth to orbit the Sun. There are several ways to measure this period, but the most common is the tropical year, which is the interval between successive passages of the Sun through the vernal equinox. The year thus computed consists of 365.242199 mean solar days, i.e., 365 days 5 hours 48 minutes 46 seconds. (The mean solar day is the average interval between two passages of the Sun across the meridian.) Unfortunately, the tropical year and the synodic month are incommensurable: 12 lunations come to 354.36706 days, almost 11 days less than a tropical year. In addition, neither the tropical year nor the synodic month is evenly divisible by the length of the day. Therefore, to compile or maintain any calendar that keeps in step with the Moon's phases or with the seasons, it is necessary to insert days at appropriate intervals. These extra days are known as intercalations. The most familiar example of an intercalation is the additional day given to February every fourth yeari.e., leap year. The origin of the calendric system in general use todaythe Gregorian calendarcan be traced back to the Roman republican calendar, which is thought to have been introduced by the fifth king of Rome, Tarquinius Priscus (616579 BC). Although somewhat similar in style to the dating system of the ancient Greeks, this calendar was more likely derived from an earlier Roman calendara lunar calendric system of 10 monthsthat supposedly was devised about 738 BC by Romulus, traditionally the founder of Rome. The Roman republican calendar consisted of 12 months with a total of 355 days. Like its model, it was basically a lunar system, short by 10 1/4 days of the 365 1/4-day tropical year. To keep it in step with the seasons, a special month was supposed to be intercalated between February 23 and 24 once every two years; but because of negligence and political interference, the intercalations were made irregularly. As a result, by 46 BC the calendar had become so hopelessly confused that Julius Caesar was forced to initiate a reform of the entire system. Caesar invited the Alexandrian astronomer Sosigenes to undertake this task. Sosigenes suggested abandoning the lunar system altogether and replacing it with a tropical year of 365 1/4 days. Further, to correct the accumulation of previous errors, a total of 90 intercalary days had to be added to 46 BC, meaning that January 1, 45 BC, occurred in what would have been the middle of March. To prevent the problem from recurring, Sosigenes suggested that an extra day be added to every fourth February. The adoption of such reformatory measures resulted in the establishment of the Julian calendar, which was used for roughly the next 1,600 years. During that time, however, the disagreement between the Julian year of 365.25 days and the tropical year of 365.242199 gradually produced significant errors. The discrepancy mounted at the rate of 11 minutes 14 seconds per year until it was a full 10 days in 1545, when the Council of Trent authorized Pope Paul III to take corrective action. No solution was found for many years. In 1572 Pope Gregory XIII agreed to issue a papal bull drawn up by the Jesuit astronomer Christopher Clavius. Ten years later, when the edict was finally proclaimed, 10 days in October were skipped to bring the calendar back in line. The length of the year was redefined as 365.2422 days, a difference of 0.0078 days per year from the Julian count, which produced a discrepancy between them amounting to 3.12 days every 400 years. Clavius had allowed for such a discrepancy in his suggestion that three out of every four centennial years, which would ordinarily be leap years, should be regarded as common years instead. This led to the practice that no centennial year could be a leap year unless it was divisible by 400. Following this rule, 1700, 1800, and 1900 were common years, but 2000 would be a leap year. These reform measures gave rise to an extremely accurate calendric system; the difference between the Gregorian calendar year and the solar year was less than half a minute. The Gregorian calendar, firmly establishing January 1 as the beginning of its year, was widely referred to as the New Style calendar, with the Julian known as the Old Style calendar. Although the Gregorian calendar is used throughout much of the world today, it was not immediately accepted everywhere. Most of the Roman Catholic states adopted the improved dating system by 1587. Some Protestant states embraced it around the beginning of the 18th century, but a number of others, such as Great Britain and its colonies, did not do so until the 1750s. Japan, China, and Russia, to name only a few, adopted the Gregorian rules much later. A few dating systems besides the Gregorian calendar still remain in use. The Muslim calendar, for example, has been retained by most Arab countries, while the traditional Hindu and Jewish calendars continue to be used for religious purposes. any system for dividing time over extended periods, such as days, months, or years, and arranging such divisions in a definite order. A calendar is convenient for regulating civil life and religious observances and for historical and scientific purposes. The word is derived from the Latin calendarium, meaning interest register, or account book, itself a derivation from calendae (or kalendae), the first day of the Roman month, the day on which future market days, feasts, and other occasions were proclaimed. The development of a calendar is vital for the study of chronology, since this is concerned with reckoning time by regular divisions, or periods, and using these to date events. It is essential, too, for any civilization that needs to measure periods for agricultural, business, domestic, or other reasons. The first practical calendar to evolve from these requirements was the Egyptian, and it was this that the Romans developed into the Julian calendar that served western Europe for more than 1,500 years. The Gregorian calendar was a further improvement and has been almost universally adopted because it satisfactorily draws into one system the dating of religious festivals based on the phases of the Moon and seasonal activities determined by the movement of the Sun. Such a calendar system is complex, since the periods of the Moon's phases and the Sun's motion are incompatible; but by adopting regular cycles of days and comparatively simple rules for their application, the calendar provides a year with an error of less than half a minute. Additional reading General works An important book on both the development of the calendar and its calculation and possible reform is Alexander Philips, The Calendar: Its History, Structure and Improvement (1921). A shorter and more up-to-date reference is the section on the calendar in the Explanatory Supplement to the Astronomical Ephemeris and the American Ephemeris and Nautical Almanac (1961, reprinted with amendments, 1977). Also useful are Frank Parise (ed.), The Book of Calendars (1982), a general reference source with a number of conversion tables; and William Matthew O'Neil, Time and the Calendars (1975). Ludwig Rohner, Kalendergeschichte und Kalender (1978), discusses the history of Western calendars. Vladimir V. Tsybulsky, Calendars of Middle East Countries (1979, originally published in Russian, 1976), examines modern calendars. Babylonian See references to special studies in E.J. Bickerman, Chronology of the Ancient World, 2nd ed. (1980). On astronomy and calendar, see Otto Neugebauer, The Exact Sciences in Antiquity, 2nd ed. (1957, reprinted 1969); and his chapter on Ancient Mathematics and Astronomy, in the History of Technology, ed. by Charles Singer et al., vol. 1 (1954). On the later Babylonian calendar cycle, see Richard A. Parker and Waldo H. Dubberstein, Babylonian Chronology 626 BCAD 75 (1956). Current bibliography is published in the quarterly review Orientalia. Other Middle Eastern Assyria Hildegard Lewy, The Cambridge Ancient History, 3rd ed., vol. 1, pt. 2, ch. 25 (1971); and, on the week, see also The Assyrian Dictionary, vol. 5 (1956). Hittites Albrecht Gtze, Kleinasien, 2nd ed. (1957). Ugarit Cyrus H. Gordon, Ugaritic Textbook (1965). Phoenicians J. Brian Peckham, The Development of the Late Phoenician Scripts (1968). Mari Archives royales de Mari XII, vol. 2 (1964). Iran E.J. Bickerman in The Cambridge History of Iran, vol. 3, pt. 2, ch. 21 (1983). Early Egyptian See Neugebauer (op. cit.); see also his Commentary on the Astronomical Treatise (1969); The Origin of the Egyptian Calendar, J. Near Eastern Stud., 1:396403 (1942); and Otto Neugebauer and Richard A. Parker (eds. and trans.), Egyptian Astronomical Texts, 3 vol. (196069). Richard A. Parker, The Calendars of Ancient Egypt (1950), is a good source on the subjectall older material is out of date; his Lunar Dates of Thutmose III and Ramesses II, J. Near Eastern Stud., 16:3943 (1957), is important for later lunar dates. H.E. Winlock, The Origin of the Ancient Egyptian Calendar, Proc. Am. Phil. Soc., 83:44764 (1940), is also an important discussion. Early Greek and Roman For the octateris, see D.R. Dicks, Solstices, Equinoxes, and the Presocratics, J. Hellenic Stud., 86:2640 (1966); see also his Early Greek Astronomy to Aristotle (1970). Sterling Dow and Robert F. Healey, A Sacred Calendar of Eleusis (1966), describes a calendar other than that of Athens. Benjamin D. Meritt, The Athenian Year (1961), contains a reconstruction of the Athenian civil years. Jon D. Mikalson, The Sacred and Civil Calendar of the Athenian Year (1975), includes useful bibliographical references. For water clocks, see Otto Neugebauer and H.B. Van Hoesen, Greek Horoscopes (1959, reprinted 1978). William Kendrick Pritchett, Ancient Athenian Calendars on Stone (1963), is good for the Athenian calendar. See also his Gaming Tables and I.G., I2, 324, Hesperia, 34:131147 (1965); and, with Otto Neugebauer, The Calendars of Athens (1947). Also useful are Bickerman (op. cit.); and Alan E. Samuel, Greek and Roman Chronology (1972). For Roman calendars, see Agnes Kirsopp Michels, The Calendar of the Roman Republic (1967, reprinted 1978); and Pierre Brind'amour, Le Calendrier romain (1983). Jewish The oldest systematic and complete book on the present fixed Jewish calendar is the work of Abraham bar Hiyya (born c. 1065), known as Savasorda of Barcelona, that bears the title Sefer ha-'Ibur. A prcis of this is contained in a section (ch. 610) in Moses Maimonides, Sanctification of the New Moon, trans. from the Hebrew by Solomon Gandz, with an Astronomical Commentary by Otto Neugebauer (1956), and supplemented in the Addenda and Corrigenda by Ernest Wiesenberg to Moses Maimonides, The Book of Seasons (1961). These treatises from the Code of Maimonides are published as vols. 11 and 14 of the Yale Judaica Series. Additional details of the Jewish calendar of both the rabbinic and sectarian varieties have been outlined by Ernest Wiesenberg in Calendar, and Jacob Licht in Sectarian Calendars, both in Encyclopaedia Judaica, vol. 5, pp 4353 (1971). Indian The most complete account of the lunarsolar calendar of India may be found in Indian Calendar, ch. 5 of the Calendar Reform Committee Report of the Government of India (1955). A good summary of the materials was published by Jean Filliozat in Notions de chronologie, an appendix of the encyclopaedic work on Indian history and culture, L'Inde classique, by Louis Renou and Jean Filliozat, vol. 2 (1953). Chinese The Chinese calendar is discussed in Joseph Needham and Wang Ling, Mathematics and the Sciences of the Heavens and the Earth, Science and Civilisation in China, vol. 3 (1959). Pre-Columbian The following are useful and authoritative references for the Mayan calendar: Sylvanus G. Morley, An Introduction to the Study of the Maya Hieroglyphs (1915, reprinted 1975); and J. Eric S. Thompson, Maya Hieroglyphic Writing: An Introduction, 3rd ed. (1971), the most complete and authoritative account. See also Floyd G. Lounsbury, Maya Numeration, Computation, and Calendrical Astronomy, Dictionary of Scientific Biography, ed. by Charles Coulston Gillispie et al., vol. 15 (1978); and Miguel Len-Portilla, Time and Reality in the Thought of the Maya (1973). For the Mexican calendar: Alfonso Caso, El Calendario Mexicano, Memorias de la Academia Mexicana de la Historia, vol. 17, no. 1 (1958); Thirteen Masterpieces of Mexican Archaeology (1938, reprinted 1976); and Los Calendarios prehispanicos (1967). See also Fray Diego Durn, Book of the Gods, and The Ancient Calendar (1971; originally published in Spanish, 1867), containing illustrated explanations of the Aztec calendar. For the Inca and related calendars: Alexander von Humboldt, Vues des Cordillres, et monuments des peuples indignes de l'Amrique, 2 vol. (1816); Alfred L. Kroeber, The Chibcha, in The Handbook of South American Indians, ed. by Julian H. Steward, vol. 2 (1946, reissued 1963); and John Howland Rowe, Inca Culture at the Time of the Spanish Conquest. Astronomy and the Calendar, also in The Handbook of South American Indians. See also Reiner Tom Zuidema, The Sidereal Lunar Calendar of the Incas, in Archaeoastronomy in the New World, ed. by A.F. Aveni (1982).For North American Indian chronologies, see the chapter by Cyrus Thomas, Calendar, in The Handbook of American Indians North of Mexico, ed. by Frederick W. Hodge, vol. 1 (1907, reprinted 1979). Colin Alistair Ronan John D. Schmidt E.J. Bickerman E.J. Wiesenberg Nicola Abdo Ziadeh J.A.B. van Buitenen Chao Lin Tatiana Proskouriakoff Ancient and religious calendar systems The Near East and the Middle East The lunisolar calendar, in which months are lunar but years are solarthat is, are brought into line with the course of the Sunwas used in the early civilizations of the whole Middle East, except Egypt, and in Greece. The formula was probably invented in Mesopotamia in the 3rd millennium BC. Study of cuneiform tablets found in this region facilitates tracing the development of time reckoning back to the 27th century BC, near the invention of writing. The evidence shows that the calendar is a contrivance for dividing the flow of time into units that suit society's current needs. Though calendar makers put to use time signs offered by naturethe Moon's phases, for examplethey rearranged reality to make it fit society's constructions. Babylonian calendars In Mesopotamia the solar year was divided into two seasons, the summer, which included the barley harvest in the second half of May or in the beginning of June, and the winter, which roughly corresponded to today's fallwinter. Three seasons (Assyria) and four seasons (Anatolia) were counted in northerly countries, but in Mesopotamia the bipartition of the year seemed natural. As late as c. 1800 BC the prognoses for the welfare of the city of Mari, on the middle Euphrates, were taken for six months. The months began at the first visibility of the New Moon, and in the 8th century BC court astronomers still reported this important observation to the Assyrian kings. The names of the months differed from city to city, and within the same Sumerian city of Babylonia a month could have several names, derived from festivals, from tasks (e.g., sheepshearing) usually performed in the given month, and so on, according to local needs. On the other hand, as early as the 27th century BC, the Sumerians had used artificial time units in referring to the tenure of some high officiale.g., on N-day of the turn of office of PN, governor. The Sumerian administration also needed a time unit comprising the whole agricultural cycle; for example, from the delivery of new barley and the settling of pertinent accounts to the next crop. This financial year began about two months after barley cutting. For other purposes, a year began before or with the harvest. This fluctuating and discontinuous year was not precise enough for the meticulous accounting of Sumerian scribes, who by 2400 BC already used the schematic year of 30 12 = 360 days. At about the same time, the idea of a royal year took precise shape, beginning probably at the time of barley harvest, when the king celebrated the new (agricultural) year by offering first fruits to gods in expectation of their blessings for the year. When, in the course of this year, some royal exploit (conquest, temple building, and so on) demonstrated that the fates had been fixed favourably by the celestial powers, the year was named accordingly; for example, as the year in which the temple of Ningirsu was built. Until the naming, a year was described as that following the year named (after such and such event). The use of the date formulas was supplanted in Babylonia by the counting of regnal years in the 17th century BC. The use of lunar reckoning began to prevail in the 21st century BC. The lunar year probably owed its success to economic progress. A barley loan could be measured out to the lender at the next year's threshing floor. The wider use of silver as the standard of value demanded more flexible payment terms. A man hiring a servant in the lunar month of Kislimu for a year knew that the engagement would end at the return of the same month, without counting days or periods of office between two dates. At the city of Mari in about 1800 BC, the allocations were already reckoned on the basis of 29- and 30-day lunar months. In the 18th century BC, the Babylonian Empire standardized the year by adopting the lunar calendar of the Sumerian sacred city of Nippur. The power and the cultural prestige of Babylon assured the success of the lunar year, which began on Nisanu 1, in the spring. When, in the 17th century BC, the dating by regnal years became usual, the period between the accession day and the next Nisanu 1 was described as the beginning of the kingship of PN, and the regnal years were counted from this Nisanu 1. It was necessary for the lunar year of about 354 days to be brought into line with the solar (agricultural) year of approximately 365 days. This was accomplished by the use of an intercalated month. Thus, in the 21st century BC, a special name for the intercalated month iti dirig appears in the sources. The intercalation was operated haphazardly, according to real or imagined needs, and each Sumerian city inserted months at will; e.g., 11 months in 18 years or two months in the same year. Later, the empires centralized the intercalation, and as late as 541 BC it was proclaimed by royal fiat. Improvements in astronomical knowledge eventually made possible the regularization of intercalation; and, under the Persian kings (c. 380 BC), Babylonian calendar calculators succeeded in computing an almost perfect equivalence in a lunisolar cycle of 19 years and 235 months with intercalations in the years 3, 6, 8, 11, 14, 17, and 19 of the cycle. The new year's day (Nisanu 1) now oscillated around the spring equinox within a period of 27 days. The Babylonian month names were Nisanu, Ayaru, Simanu, Du'uzu, Abu, Ululu, Tashritu, Arakhsamna, Kislimu, Tebetu, Shabatu, Adaru. The month Adaru II was intercalated six times within the 19-year cycle but never in the year that was 17th of the cycle, when Ululu II was inserted. Thus, the Babylonian calendar until the end preserved a vestige of the original bipartition of the natural year into two seasons, just as the Babylonian months to the end remained truly lunar and began when the New Moon was first visible in the evening. The day began at sunset. Sundials and water clocks served to count hours. The influence of the Babylonian calendar was seen in many continued customs and usages of its neighbour and vassal states long after the Babylonian Empire had been succeeded by others. In particular, the Jewish calendar in use at relatively late dates employed similar systems of intercalation of months, month names, and other details (see below The Jewish calendar). The Jewish adoption of Babylonian calendar customs dates from the period of the Babylonian Exile in the 6th century BC. The Western calendar and calendar reforms The calendar now in general worldwide use had its origin in the desire for a solar calendar that kept in step with the seasons and possessed fixed rules of intercalation. Because it developed in Western Christendom, it had also to provide a method for dating movable religious feasts, the timing of which had been based on a lunar reckoning. To reconcile the lunar and solar schemes, features of the Roman republican calendar and the Egyptian calendar were combined. The Roman republican calendar was basically a lunar reckoning and became increasingly out of phase with the seasons as time passed. By about 50 BC the vernal equinox that should have fallen late in March fell on the Ides of May, some eight weeks later, and it was plain that this error would continue to increase. Moreover, the behaviour of the Pontifices (see above The early Roman calendar) made it necessary to seek a fixed rule of intercalation in order to put an end to arbitrariness in inserting months. In addition to the problem of intercalation, it was clear that the average Roman republican year of 366.25 days would always show a continually increasing disparity with the seasons, amounting to one month every 30 years, or three months a century. But the great difficulty facing any reformer was that there seemed to be no way of effecting a change that would still allow the months to remain in step with the phases of the Moon and the year with the seasons. It was necessary to make a fundamental break with traditional reckoning to devise an efficient seasonal calendar. The Julian calendar In the mid-1st century BC Julius Caesar invited Sosigenes, an Alexandrian astronomer, to advise him about the reform of the calendar, and Sosigenes decided that the only practical step was to abandon the lunar calendar altogether. Months must be arranged on a seasonal basis, and a tropical (solar) year used, as in the Egyptian calendar, but with its length taken as 365 1/4 days. To remove the immense discrepancy between calendar date and equinox, it was decided that the year known in modern times as 46 BC should have two intercalations. The first was the customary intercalation of the Roman republican calendar due that year, the insertion of 23 days following February 23. The second intercalation, to bring the calendar in step with the equinoxes, was achieved by inserting two additional months between the end of November and the beginning of December. This insertion amounted to an addition of 67 days, making a year of no less than 445 days and causing the beginning of March, 45 BC in the Roman republican calendar, to fall on what is still called January 1 of the Julian calendar. Previous errors having been corrected, the next step was to prevent their recurrence. Here Sosigenes' suggestion about a tropical year was adopted and any pretense to a lunar calendar was rejected. The figure of 365.25 days was accepted for the tropical year, and, to achieve this by a simple civil reckoning, Caesar directed that a calendar year of 365 days be adopted and that an extra day be intercalated every fourth year. Since February ordinarily had 28 days, February 24 was the sixth day (using inclusive numbering) before the Kalendae, or beginning of March, and was known as the sexto-kalendae; the intercalary day, when it appeared, was in effect a doubling of the sexto-kalendae and was called the bis-sexto-kalendae. This practice led to the term bissextile being used to refer to such a leap year. The name leap year is a later connotation, probably derived from the Old Norse hlaupa (to leap) and used because, in a bissextile year, any fixed festival after February leaps forward, falling on the second weekday from that on which it fell the previous year, not on the next weekday as it would do in an ordinary year. Apparently, the Pontifices misinterpreted the edict and inserted the intercalation too frequently. The error arose because of the Roman practice of inclusive numbering, so that an intercalation once every fourth year meant to them intercalating every three years, because a bissextile year was counted as the first year of the subsequent four-year period. This error continued undetected for 36 years, during which period 12 days instead of nine were added. The emperor Augustus then made a correction by omitting intercalary days between 8 BC and AD 8. As a consequence, it was not until several decades after its inception that the Julian calendar came into proper operation, a fact that is important in chronology but is all too frequently forgotten. It seems that the months of the Julian calendar were taken over from the Roman republican calendar but were slightly modified to provide a more even pattern of numbering. The republican calendar months of March, May, and Quintilis (July), which had each possessed 31 days, were retained unaltered. Although there is some doubt about the specific details, changes may have occurred in the following way. Except for October, all the months that had previously had only 29 days had either one or two days added. January, September, and November received two days, bringing their totals to 31, while April, June, Sextilis (August), and December received one day each, bringing their totals to 30. October was reduced by one day to a total of 30 days and February increased to 29 days, or 30 in a bissextile year. With the exception of February, the scheme resulted in months having 30 or 31 days alternately throughout the year. And in order to help farmers, Caesar issued an almanac showing on which dates of his new calendar various seasonal astronomical phenomena would occur. These arrangements for the months can only have remained in force for a short time, because in 8 BC changes were made by Augustus. In 44 BC, the second year of the Julian calendar, the Senate proposed that the name of the month Quintilis be changed to Julius (July), in honour of Julius Caesar, and in 8 BC the name of Sextilis was similarly changed to Augustus (August). Perhaps because Augustus felt that his month must have at least as many days as Julius Caesar's, February was reduced to 28 days and August increased to 31. But because this made three 31-day months (July, August, and September) appear in succession, Augustus is supposed to have reduced September to 30 days, added a day to October to make it 31 days, reduced November by one day to 30 days, and increased December from 30 to 31 days, giving the months the lengths they have today. Several scholars, however, believe that Caesar originally left February with 28 days (in order to avoid affecting certain religious rites observed in honour of the gods of the netherworld) and added two days to Sextilis for a total of 31; January, March, May, Quintilis, October, and December also had 31 days, with 30 days for April, June, September, and November. The subsequent change of Sextilis to Augustus therefore involved no addition of days to the latter. The Julian calendar retained the Roman republican calendar method of numbering the days of the month. Compared with the present system, the Roman numbering seems to run backward, for the first day of the month was known as the Kalendae, but subsequent days were not enumerated as so many after the Kalendae but as so many before the following Nonae (nones), the day called nonae being the ninth day before the Ides (from iduare, meaning to divide), which occurred in the middle of the month and were supposed to coincide with the Full Moon. Days after the Nonae and before the Ides were numbered as so many before the Ides, and those after the Ides as so many before the Kalendae of the next month. It should be noted that there were no weeks in the original Julian calendar. The days were designated either dies fasti or dies nefasti, the former being business days and days on which the courts were open; this had been the practice in the Roman republican calendar. Julius Caesar designated his additional days all as dies fasti, and they were added at the end of the month so that there was no interference with the dates traditionally fixed for dies comitiales (days on which public assemblies might be convened) and dies festi and dies feriae (days for religious festivals and holy days). Originally, then, the Julian calendar had a permanent set of dates for administrative matters. The official introduction of the seven-day week by Emperor Constantine I in the 4th century AD disrupted this arrangement. It appears, from the date of insertion of the intercalary month in the Roman republican calendar and the habit of designating years by the names of the consuls, that the calendar year had originally commenced in March, which was the date when the new consul took office. In 222 BC the date of assuming duties was fixed as March 15, but in 153 BC it was transferred to the Kalendae of January, and there it remained. January therefore became the first month of the year, and in the western region of the Roman Empire, this practice was carried over into the Julian calendar. In the eastern provinces, however, years were often reckoned from the accession of the reigning emperor, the second beginning on the first New Year's day after the accession; and the date on which this occurred varied from one province to another.