Calendar
2 of the 7 encyclopedias on this shelf carry an entry for Calendar. Both are reproduced below, so you can see where they agree and where they differ.
Collier's New Encyclopedia (1921)
a distribution or division of time into periods adapted to the purposes of civil life; also table or a register of such divisions, exhibiting the order in which the seasons, months, festivals, and holidays succeed each other in the year. The most remarkable calendars are: 1. The Hebrew calendar. The year of the Jews was a lunar one, being composed of 354 days, divided into 12 months, which had alternately 29 and 30 days. In order to make this lunar year accord with the solar year, the Hebrews supplied, seven times in 19 years, an intercalary month of 29 days. Each month was divided into periods of seven days, or weeks, the Saturday being celebrated under the name of Sabbath. 2. The calendar of the Greeks, whose year was likewise lunar, and composed of 12 months, containing alternately 29 and 30 days. To accommodate this year to the solar one, the Greeks added every supplementary month. two years a Each month was divided into three decades. 3. The Roman, or Julian calendar. The Roman year, under Romulus, contained only 10 months, or 304 days. Under Numa, however, the year was extended to 12 months, or 355 days; but, although nominally thus defined, the calendar did not in reality fix anything more precise than the commencement of the months and seasons; and through the ignorance or negligence of the priests, the utmost derangement subsequently arose. To obviate this condition, Julius Cæsar, in 46 B. C., effected a reform, by the introduction of the Julian calendar, in which the length of the solar year was fixed at 365 days, to which was added, every four years, a day called bissextile. This_calendar was adopted not only by the Romans, but also by all the modern nations, and remained in use until the introduction of the calendar of Gregory XIII. The Roman year had 12 months, each being being divided into unequal parts by the Calends, Nones, and Ides. 4. The Gregorian calendar. This mode of distributing time was the result of the reform inaugurated by Gregory XIII. It came into operation in October, 1582. The Greeks and Russians have refused to adopt the Gregorian calendar, retain ing the old style, or Julian calendar. Hence it is necessary to deduct 12 days from the new style in order to make it agree with the old. 5. The Ecclesiastical calendar. The adaptation of the civil to the solar year is attended with no difficulty; but the church calendar, for regulating the movable feasts, imposes conditions less easily satisfied. The early Christians borrowed a portion of their ritual from the Jews. The Jewish year was luni-solar; that is to say, depended on the moon as well as on the sun. Easter, the principal Christian festival, in imitation of the Jewish passover, was celebrated about the time of the full moon. Differences of opinion, and consequently disputations, soon arose as to the proper day on which the celebration should be held. In order to put an end to an unseemly contention, the Council of Nice laid down a specific rule, and ordered that Easter should always be celebrated on the Sunday which immediately follows the full moon that happens upon, or next after, the day of the vernal equinox. In order to determine Easter, according to this rule, for any particular year, it is necessary to reconcile three periods, namely, the week, the lunar month, and the lunar year. To find the day of the week on which any given day of the year falls, it is necessary to know on what day of the week the year began. In the Julian calendar this was easily found by means of a short period or cycle of 28 years, after which the year begins with the same day of the week. In the Gregorian calendar this order is interrupted by the omission of the intercalation in the last year of the century. The connection of the lunar month with the solar year is an ancient problem for the resolution of which the Greeks invented cycles and periods, which remained in use with some modifications till the time of the Gregorian reformation. The author of the Gregorian calendar, Luigi Lilio Ghiraldi, or, as he is frequently called, Aloysius Lilius, employed for the same purpose a set of numbers called epacts. 6. New French calendar. A new reform of the calendar was attempted to be introduced in France during the period of the first revolution. This was adopted by a decree of the National Convention of October, 1793. The year was therein divided into 12 months, of 30 days each, 5 complementary, or "sansculottides" days, being added at the end of each year. The commencement of the year was fixed at midnight of September 22d (the autumnal equinox), and retrospectively, the new year, or Year I. of the Republic, began on Sept. 22, 1792. Fresh names were given to the months and the days, the titles of the months being, for the autumn season, Vendémiaire, Brumaire, and Frimaire; for the winter season, Nivîse, Pluviôse, and Ventose; for the spring season, Germinal, Floréal, and Prairial; and for the summer season, Messidor, Thermidor, and Fructidor: these names having reference to agricultural labors, or the state of nature in the different seasons of the year. Each month was divided into three decades (10 days each), each day bearing, instead of the name of a saint, that of an agricultural product, implement, or animal useful in cultivating the earth. This calendar remained in force during 13 years, and was abolished by decree of Napoleon I., on Jan. 1, 1806.
Aiton's Encyclopedia (1910)
2026 Editor's Note: This page uses language about other peoples, religions, or nationalities that was commonplace when the book was published and is offensive by today's standards. The text has been left exactly as it was printed, rather than cut or softened, so that the historical record — including how ordinary such language once was — is preserved. (Ed: ET 2026-07-22) the orderly record of time. About the only units of time in use among savage people are the day and the moon. Such a moon is the rice moon, or moon for gathering wild rice. Another may be the sore-eyes moon, when the smoke of the tepee and glare of the snow bring on sore eyes. Religious ceremonies based on the time of the moon carried forward a time record, based on the month, far into civilization. Civilization reckons time in years. As the phases of the moon do not come out even with the end of the year, a year composed of new moons is out of harmony with a year based on the seasons. We trace our calendar to the Egyptians. Whether they understood the revolution of the earth about the sun or not cannot be determined, but they noted the return of the sun to a certain position at regular intervals. This they fixed at 365 1/4 days, less a fraction. They established a system of leap years and possessed a calendar of months. This Egyptian calendar was adopted by the Romans. The pontiffs who had charge of festivals and religious observances had charge also of the official calendar. In 45 B. C. the Roman calendar had run behind nearly three months. The spring equinox was scheduled to come off in June. Caesar reformed the calendar by decreeing that the year 46, "the last year of confusion," should be prolonged to 445 days. He further ordered that three years out of four should have 365 days, and that each fourth year,--that is, each year divisible by four,--should have 366 days. This is called the Julian Calendar. According to it, each century is about three-fourths of a day too long. The new century should begin a day sooner three centuries out of four, a loss of three days every 400 years. In this way each century began farther and farther behind time. Pope Gregory, finding that the church festivals were noticeably changing in season, decreed, 1582, that the day following the fourth of October of that year should be recorded the fifteenth instead of the fifth day of the month; and to avoid future difficulty he further decreed that the last year of each century three times out of four should not be a leap year ; or, put in another way, that only such century years be reckoned leap years as are divisible by 400. Accordingly, 1700, 1800, and 1900 had but 365 days, but the year 2000 will be assigned 366 days. This is known as the Gregorian Calendar. The Gregorian Calendar was adopted in all Catholic countries and by most Protestant countries at once. England waited until 1751; then fell in with a statute that the day following the second of September be reckoned the fourteenth instead of the third. The Gregorian Calendar is followed by the commercial world; that is to say, everywhere save in Russia, in which the Greek Church adheres to the Julian Calendar for fear of impiety in setting forward church festivals. The Russian dates are thirteen days behind ours. When Alaska was taken over the difference in reckoning was added, so that the official records of Alaska would indicate that it never had a certain thirteen days at all.