This section gathers the calendars of the world and their parts: solar, lunar and lunisolar systems with their months, intercalations and eras, the Hebrew and Islamic months, the Maya haab and Long Count, the Chinese earthly branches, and the tithis and related units of the Hindu lunar calendar, among others.
A calendar is where a cosmology becomes practical. The decision to follow the Sun, the Moon, or both, and how to reconcile them, sets the rhythm of festivals, fasts and work, and every solution carries consequences, the Islamic lunar year drifting through the seasons, the Hebrew and Chinese lunisolar years adding a month to catch up.