Definition of: calendar

(kal′ən·dər) noun
1. A systematic arrangement of subdivisions of time, as years, months, days, weeks, etc.
2. An almanac.
3. A schedule or list of things or events classified or chronologically arranged: a calendar of causes for trial in court.
4. Obs. A guide; example; model.
—v.t. To register in a calendar or list; place in the calendar of saints; digest and index, as documents. ◆ Homophone: calender. [<L calendarium account book <calendae calends]
—Chinese calendar
An ancient calendar, no longer in official use, with days and years reckoned in cycles of sixty. Each year consists of twelve lunar months, with adjustment to the solar year by periodic intercalation.
—ecclesiastical calendar
A lunisolar calendar reckoning the year from the first Sunday in Advent: used for regulating the dates of church feasts.
—Gregorian calendar
The calendar now in general use in most parts of the world; first prescribed in 1582 by Pope Gregory XIII to correct the Julian year to the solar year; adopted in England Sept. 3/14, 1752, the first being the Old Style (O.S.) date and the last being the New Style (N.S.). (Thus, although George Washington's birthday is commemorated on February 22, he was born on February 11, 1732, by the Old Style calendar.)
—Hebrew calendar
The present–day calendar of the Jews, based on a lunar month, and adjusted to the solar year by intercalating the month Veadar between Adar and Nisan 7 times in a 19–year cycle. The months, having alternately 30 and 29 days, are Tishri, Heshwan, Kislew, Tebet, Shebat, Adar, Nisan, Iyyar, Siwan, Tammuz, Ab, and Elul; Heshwan and Kislew, however, may add or lose a day respectively as needed. The year now begins on Tishri 1, though anciently it began in Nisan. The Hebrew calendar reckons the creation at 3760 years 3 months B.C., as compared with Archbishop Ussher's 4004 B.C.
—Hindu calendar
A solar calendar, reckoned in 12 months, each beginning when the sun enters a new sign of the zodiac.
—Julian calendar
The calendar prescribed by Julius Caesar, which, though using the bissextile year, was in error one day in 128 years. The months, after some changes by Augustus, had the length now in use in Europe and America.
—Mohammedan calendar
A lunar calendar of 12 months dating from A.D. 622 (July 15), the year of the Hegira. There is no seasonal intercalation, the seasons retrogressing in a period of 32 1/2 years. The names of the months, alternately 29 and 30 days, are Muharram (30 days), Saphar, Rabia 1, Rabia 2, Jomada 1, Jomada 2, Rajab, Shaaban, Ramadan, Shawwal, Dulkaada, and Dulheggia.
—perpetual calendar
A calendar by which the day of the week for any given date may be ascertained during a widely extended period of time.
—Republican or Revolutionary calendar
The calendar instituted on Oct. 5, 1793, by the first French Republic, and abolished Dec. 31, 1805. Its scheme divided the year into 12 months of 30 days each, with five (in leap years, six) supplementary days (sansculottides) at the end of the last month. The first year (Year I) began Sept. 22, 1792. The months were: Vendémiaire, Brumaire, Frimaire, Nivose, Pluviose, Ventose, Germinal, Floréal, Prairial, Messidor, Thermidor (or Fervidor), and Fructidor.
—Roman calendar
A lunar calendar, attributed to Numa. The day of the new moon was the calends, and the day of the full moon the ides (the 13th or 15th of the month). Days were reckoned backward from these dates and from the nones, ninth day before the ides by inclusive reckoning.
—world calendar
A proposed reformed calendar designed to equalize the lengths of the quarters of the year, each to have one month of 31 and two of 30 days. It provides for extra days to conform to solar time.