
List of calendars

This is a list of calendars. Included are historical calendars as well as proposed ones. Historical calendars are often grouped into larger categories by cultural sphere or historical period; thus O'Neil (1976) distinguishes the groupings Egyptian calendars (Ancient Egypt), Babylonian calendars (Ancient Mesopotamia), Indian calendars (Hindu and Buddhist traditions of the Indian subcontinent), Chinese calendars and Mesoamerican calendars. 
These are not specific calendars but series of historical calendars undergoing reforms or regional diversification.
In Classical Antiquity, the Hellenic calendars inspired the Roman calendar, including the solar Julian calendar introduced in 45 BC. Many modern calendar proposals, including the Gregorian calendar itself, are in turn modifications of the Julian calendar.
List of calendars.
In the list below, specific calendars are given, listed by calendar type (solar, lunisolar or lunar), time of introduction (if known), and the context of use and cultural or historical grouping (if applicable).
Regional or historical groups: Hijri calendar, Mayan, Aztecan, Egyptian, Mesopotamian, Iranian, Hindu, Buddhist, Pre-Columbian Mesoamerican, Hellenic, Julian or Gregorian-derived.
Calendars fall into four types, lunisolar, solar, lunar, seasonal, besides calendars with "years" of fixed length, with no intercalation. Most pre-modern calendars are lunisolar. The seasonal calendars rely on changes in the environment rather than lunar or solar observations. The Islamic and some Buddhist calendars are lunar, while most modern calendars are solar, based on either the Julian or the Gregorian calendars.
Some "calendars" listed are identical to the Gregorian calendar except for substituting regional month names or using a different calendar era.
For example, the Thai solar calendar (introduced 1888) is the Gregorian calendar using a different era (543 BC) and different names for the Gregorian months (Thai names based on the signs of the zodiac).
Variant month names.
Regional or historical names for lunations or Julian/Gregorian months