Calendars

36 entries. Click any to see everything it connects to.

The calendars by which traditions count time: solar, lunar and lunisolar systems including the Gregorian, Julian, Hebrew, Islamic, Hindu, Chinese, Maya and Zoroastrian calendars, with their months, intercalations and eras. Each entry records the system's structure, where it is used, and how it relates to the civil calendar, including whether it reconciles a lunar month against the solar year with an inserted leap month or a fixed leap day. Calendars are where cosmology becomes practical, since the day a festival falls on is settled here, and a calendar's own reckoning has repeatedly become a point of religious authority and dispute in its own right, as in the historic controversies over dating Easter.

Facts

Overview

Entries in the Atlas: 36
What Defines This Grouping: Whole calendar systems, as against the months, day-units, cycles and eras they are built from, which the atlas holds as their own categories. No single origin, people or date belongs to this grouping. 1

Structure

Structure: Three workable answers to one astronomical problem: a solar year holds the seasons and lets the months drift from the Moon; a lunar year holds the months and drifts through the seasons; a lunisolar year intercalates a month to hold both. 1

Sources

Calendrical Calculations: The Ultimate Edition Edward M. Reingold and Nachum Dershowitz, 2018

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How Traditions Count Time

A calendar is a system for organising and counting days into larger units (weeks, months, years and eras), and this category holds the calendars of the world's traditions: solar, lunar and lunisolar, with their months, intercalations and reckonings of the year. Each entry records a system's structure, where and by whom it is used, and how it relates to the common civil calendar.

The fundamental problem every calendar solves is that the natural cycles do not divide evenly: the year is not a whole number of days or of lunar months, so any calendar must choose which cycle to follow and how to reconcile it with the others.

Solar, lunar, lunisolar

A solar calendar (like the Gregorian) follows the Sun and keeps the seasons fixed but lets the months drift from the Moon; a lunar calendar (like the Islamic) follows the Moon and lets the year drift through the seasons; a lunisolar calendar (like the Hebrew, Chinese and Hindu) follows the Moon but adds a leap month periodically to stay in step with the Sun. Each choice shapes a tradition's festivals and life.

The atlas describes each calendar's rule, its months and eras, and its religious use. The individual months and units of particular calendars (Hebrew, Islamic, Maya and others), are treated in their own categories under Calendars & Time.