Cosma / Communication / Knowledge / Realm / Chronology / Calendar


Jeremiah Warren (YouTube Channel)
Jeremiah Warren (Official Website)


calendar : a system for fixing the beginning, length, and divisions of the civil year and arranging days and longer divisions of time (as weeks and months) in a definite order — Merriam-Webster   See also OneLook

Illustrated Professional Dictionary of Horology (Federation of the Swiss Watch Industry)


Roget’s II (, Merriam-Webster Thesaurus, Visuwords


Calendar is a system of organizing days for social, religious, commercial, or administrative purposes. This is done by giving names to periods of time, typically days, weeks, months, and years. A date is the designation of a single, specific day within such a system. Periods in a calendar (such as years and months) are usually, though not necessarily, synchronized with the cycle of the sun or the moon. Many civilizations and societies have devised a calendar, usually derived from other calendars on which they model their systems, suited to their particular needs. A calendar is also a physical device (often paper) or computer program. — Wikipedia (List of Calendars)

Introduction to Calendars (Encyclopædia Britannica)
Calendars (Encyclopædia Britannica)

Calendopaedia (Michael Astbury)
Calendars New and Old (Hermetic Systems)

Calendars (Exactly What Is Time?)
Calendar (Time and Date)

Calendar Converter (Fourmilab)
Rosetta Calendar (Scott E. Lee)

Calendars (Eric Weisstein’s World of Science, Wolfram Research)
Date & Time Computations (Wolfram Alpha)



Articles about Calendars (Big Think)



Perpetual calendar is a calendar valid for many years, usually designed to allow the calculation of the day of the week for a given date in the future. For the Gregorian and Julian calendars, a perpetual calendar typically consists of one of two general variations:
(1) 14 one-year calendars, plus a table to show which one-year calendar is to be used for any given year. These one-year calendars divide evenly into two sets of seven calendars: seven for each common year (year that does not have a February 29) that starts on each day of the week, and seven for each leap year that starts on each day of the week, totaling fourteen.
(2) Seven (31-day) one-month calendars (or seven each of 28–31 day month lengths, for a total of 28) and one or more tables to show which calendar is used for any given month. Some perpetual calendars’ tables slide against each other, so that aligning two scales with one another reveals the specific month calendar via a pointer or window mechanism. The seven calendars may be combined into one, either with 13 columns of which only seven are revealed, or with movable day-of-week names. — Wikipedia

Grand Illusions (Hendrik Ball, YouTube Channel)
Grand Illusions (Hendrik Ball, Official Website)



Calendar Gifts (Zazzle)
Calendar (Etsy)




Ancient Calendars (A Walk Through Time, NIST Physical Measurement Laboratory)
Calendars through the Ages (Claus Tøndering, Web Exhibits)

Gregorian Calendar (Eric Weisstein’s World of Astronomy, Wolfram Research)
Gregorian Calendar (Time and Date)
Gregorian Calendar (Wikipedia)


Museum of Creative Calendar Design (Unicorn Graphics)


DDC: 529.3 Calendars (Library Thing)
Subject: Calendars (Library Thing)

Subject: Calendars (Open Library)

LCC: CE 73 Calendars (UPenn Online Books)

LCC: CE 73 Calendars (Library of Congress)
Subject: Calendars (Library of Congress)

Subject: Calendars (WorldCat)




5 Activities Using a Classroom Calendar (Teach Start)

MERLOT: Multimedia Educational Resource for Learning and Online Teaching
OER Commons: Open Educational Resources



Calendar (JSTOR)
Calendar (Farmers’ Almanac)
Calendar (Time & Date)




Calendar (Tim Hunkin, The Rudiments of Wisdom Encyclopedia)


OEDILF: The Omnificent English Dictionary In Limerick Form




Here are links to pages about closely related subjects.

Knowledge Realm

Geography Navigation, Map
Chronology Calendar, Clock

Realms Cosmological, Physical, Terrestrial, Anthropological, Mystical

See also Zoom



1.   The resources on this page are are organized by a classification scheme developed exclusively for Cosma.