Astronomy: Calendars and Timekeeping

A proposal for a non-sectarian, culturally neutral calendar system.

The worldwide interactive online astronomical/space calendar and calculator - for friends of astronomy, as well as astronomers.

Extensive descriptions of many astronomical time keeping systems, with information on time zones and Julian day numbers.

Applets related to calendars and keeping time, including sidererial time.

Second full moon in a month, or third full moon in a single season?

Britannica.com explores the history of timekeeping, from sundials to cesium atomic clocks.

Articles on the Gregorian and Julian calendars, the ISO date format, the Julian day number system, the Maya calendar, the Goddess lunar calendar, the Liberalia Triday Calendar and C functions for date conversion; plus software for calendrical conversion.

History and FAQs of calendars, from ancient Rome to outer space. Including Julian, Gregorian, Jewish, Islamic, Chinese, and Mayan.

The Encyclopaedia of Calendars.

Published by Cambridge University Press. Gives a unified algorithmic presentation of the Gregorian, ISO, Julian, Coptic, Ethiopic, and Islamic civil calendars.