American Heritage Dictionary Entry: calendar HOW TO USE THE DICTIONARY To look up an entry in The American Heritage Dictionary of the English Language, use the search window above. For best results, after typing in the word, click on the “Search” button instead of using the “enter” key. Some compound words (like bus rapid transit, dog whistle, or identity theft) don’t appear on the drop-down list when you type them in the search bar. For best results with compound words, place a quotation mark before the compound word in the search window. guide to the dictionary THE USAGE PANEL The Usage Panel is a group of nearly 200 prominent scholars, creative writers, journalists, diplomats, and others in occupations requiring mastery of language. Annual surveys have gauged the acceptability of particular usages and grammatical constructions. The Panelists NEED HELP SOLVING A CROSSWORD PUZZLE? Go to our Crossword Puzzle Solver and type in the letters that you know, and the Solver will produce a list of possible solutions. -- AMERICAN HERITAGE DICTIONARY APP The new American Heritage Dictionary app is now available for iOS and Android. THE AMERICAN HERITAGE DICTIONARY BLOG The articles in our blog examine new words, revised definitions, interesting images from the fifth edition, discussions of usage, and more. OPEN DICTIONARY PROJECT Share your ideas for new words and new meanings of old words! Start Sharing Now! -- See word lists from the best-selling 100 Words Series! Find out more! INTERESTED IN DICTIONARIES? Check out the Dictionary Society of North America at http://www.dictionarysociety.com cal·en·dar (kălən-dər) Share: Tweet n. 1. Any of various systems of reckoning time in which the beginning, length, and divisions of a year are defined, sometimes along with multiyear cycles. 2. A table showing the months, weeks, and days in at least one specific year. 3. A schedule of events. 4. An ordered list of matters to be considered:the bills on a legislative calendar. 5. Chiefly British A catalog of a university. tr.v. cal·en·dared, cal·en·dar·ing, cal·en·dars To enter in a calendar; schedule. [Middle English calender, from Old French calendier, from Late Latin kalendārium, from Latin, account book, from kalendae, calends (from the fact that monthly interest was due on the calends); see kelə-2 in the Appendix of Indo-European roots.] THREE PRINCIPAL CALENDARS The Gregorian calendar is now in use as the civil calendar throughout most of the world. The Jewish calendar is the official calendar of the Jewish religious community. The Islamic calendar is the official calendar in many Muslim countries. Each calendar listed below begins with the first month of the year and includes the number of days each month contains. Many months have a variable number of days, as described below.GREGORIANJEWISHISLAMICThe Gregorian calendar, introduced in 1582 by Pope Gregory XIII, is a corrected form of the Julian calendar. It is based on a solar year of 365 days. Every fourth year is a leap year of 366 days except for centenary years not evenly divisible by 400.The Jewish year consists of twelve months defined by lunar cycles, with some years having a thirteenth month so that seasonal festivals stay aligned with the solar year. For religious purposes Nisan is the first month, but the New Year is celebrated in Tishri. In leap years Adar is known as Adar Sheni.The Islamic calendar is based on the lunar year and contains 354 or 355 days. The number of days in each month varies with the lunar cycle. The beginning of the year retrogresses through the solar year, completing a full cycle every 32.5 years.MonthsNumber of DaysMonthsNumber of DaysMonthsNumber of DaysJanuary 31Nisan (Mar-Apr)30Muharram 29 or 30February 28 or 29Iyar (Apr-May)29Safar 29 or 30March 31Sivan (May-Jun)30Rabi I 29 or 30April 30Tammuz (Jun-Jul)29Rabi II 29 or 30May 31Av (Jul-Aug)30Jumada I 29 or 30June 30Elul (Aug-Sep)29Jumada II 29 or 30July 31Tishri (Sep-Oct)30Rajab 29 or 30August 31Heshvan (Oct-Nov)29 or 30Shaʾban 29 or 30September 30Kislev (Nov-Dec)29 or 30Ramadan 29 or 30October 31Tevet (Dec-Jan)29Shawwal 29 or 30November 30Shevat (Jan-Feb)30Dhu'l-Qa'dah 29 or 30December31Adar Rishon(leap year only)30Dhu'l-Hijjah 29 or 30Adar (Feb-Mar)29 The American Heritage® Dictionary of the English Language, Fifth Edition copyright ©2022 by HarperCollins Publishers. All rights reserved. Indo-European & Semitic Roots Appendices Thousands of entries in the dictionary include etymologies that trace their origins back to reconstructed proto-languages. You can obtain more information about these forms in our online appendices: Indo-European Roots Semitic Roots The Indo-European appendix covers nearly half of the Indo-European roots that have left their mark on English words. A more complete treatment of Indo-European roots and the English words derived from them is available in our Dictionary of Indo-European Roots. 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