Calendars and Timekeeping
ACalendar.com
The calendar has many options with a standard monthly interface, including sunrise, sunset, and Moon phases.
Annus Novus Decimal Calendar
A proposal for a non-sectarian, culturally neutral calendar system.
Astro Portal - CalSKY
The worldwide interactive online astronomical/space calendar and calculator - for friends of astronomy, as well as astronomers.
Astronomical Time Keeping
Extensive descriptions of many astronomical time keeping systems, with information on time zones and Julian day numbers.
Astronomy by JavaScript: Sun Calculators and More
Applets related to calendars and keeping time, including sidererial time.
Astronomy Calendar
Features different views of the night sky, constellations, stars, planets, and other celestial wonders.
Britannica.com - Clockworks: From Sundials to the Atomic Second
Britannica.com explores the history of timekeeping, from sundials to cesium atomic clocks.
Calendar Studies
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 …
Calendars through the Ages
History and FAQs of calendars, from ancient Rome to outer space. Including Julian, Gregorian, Jewish, Islamic, Chinese, and Mayan.
Calendrical Calculations
Published by Cambridge University Press. Gives a unified algorithmic presentation of the Gregorian, ISO, Julian, Coptic, Ethiopic, and Islamic civil calendars.
Greenwich Time: Home of World Time (GMT) since 1884
Complete guide to times in every time zone in the world.
Hindu Calendar Dates 52nd Century
Explains the cosmological and astronomical influences in creating the Indian calendar.
Indian Moons
A list of many American Indian tribe's names for months, days, and other calendar related information.
Julian Day Numbers
An explanation of the Julian day number system used by astronomers and calendricists.
Leap Seconds
Civil time is occasionally adjusted by one second increments called leap seconds. A detailed explanation of what a second actually is, and why leap seconds are necessary.
LunarCal - A Perpetual Chinese Lunar Calendar
LunarCal is a 160-year perpetual Chinese Lunar Calendar for 1900 to 2060. Chinese festivals are listed and the moon phase is displayed.
Lunisolar Calendar
Lunar calendar with lunations, from new moon to new moon, instead of months. Moon phase on each day. Chinese, Jewish, and Islamic months. Eclipses, meteors, planets, star charts. C…
Maya Calendar 2000
The calendar was the center of Maya life and their greatest cultural achievement. To carry out their astronomical calculations they developed a sophisticated mathematical system. T…
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