Calendars are an essential element in date tracking.

There are a number of different calendar systems in use today globally. While the Gregorian calendar has achieved relatively universal status, some are used in specific locations, such as the Hebrew, Chinese and Japanese calendars, some are used for specific purposes, such as the Buddhist calendars for religious and cultural reasons, and a large number of them relegated to historic archives and bibliography.

With multiple calendar systems in common use across the international community, it is necessary for a number of applications to identify calendar systems used for particular dates and times, including for computing, archiving, communication and bibliography.

This standard sets out the necessary procedures to maintain the registry of calendar systems.

This document provides a list of codes to represent calendar systems and the corresponding maintenance procedures.

The codes were devised for usage of any application requiring the expression of calendar systems in coded form, including for data interchange.