Construction of a KALENDAR, or Almanac. 1. Compute the sun's and moon's place for each day of the year; or take them from ephemerides. 2. Find the dominical letter, and, by means thereof, distribute the kalendar into weeks. 3. Compute the time of Easter, and thence fix the other moveable feasts. 4. Add the immovable feasts, with the names of the martyrs. 5. To every day add the sun's and moon's place, with the rising and setting of each luminary; the length of day and night; the crepuscula, and the aspects of the planets. 6. Add, in the proper places, the chief phases of the moon, and the sun's entrance into the cardinal-points; i. e. the solstices and equinoxes; together with the rising and the setting, especially heliacal, of the planets and chief fixed stars. See ASTRONOMY.
The duration of the crepuscula, or the end of the evening and beginning of the morning twilight, together with the sun's rising and setting, and the length of days, may be transferred from the calendars of one year, into those of another; the differences in the several years being too small to be of any consideration in civil life.
Hence it appears, that the construction of a kalendar has nothing in it of mystery, or difficulty, if tables of the heavenly motions be at hand.
Some divide calendars or almanacs into public and private, perfect and imperfect; others into heathen and Christian.
Public almanacs are those of a larger size, usually hung up for common or family use; private are those of a smaller kind, to be carried about either in the hand, inscribed on a staff, or in the pocket; perfect, those which have the dominical letters as well as primes and feasts inscribed on them; imperfect, those which have only the primes and immovable feasts. Till about the fourth century, they all carry the marks of heathenism; from that age to the seventh, they are generally divided between heathenism and Christianity.
Almanacs are of somewhat different composition, some containing more points, others fewer. The essential part is the kalendar of months and days, with the risings and setting of the sun, age of the moon, &c. To these are added various parerga, astronomical, astrological, meteorological, chronological, and even
political, rural, medical, &c. as calculations, and accounts of eclipses, solar ingresses, aspects, and configurations of the heavenly bodies, lunations, heliocentric and geocentric motions of the planets, prognostics of the weather, and predictions of other events, tables of the planetary motions, the tides, terms, interest, twilight, equation, kings, &c.