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.
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.
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.
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.
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…
Rosetta Calendar
An online handy tool for converting to and from the Gregorian, Julian and Jewish calendars.
The Julian and Gregorian Calendars
Explanations of the Julian Calendar, the Gregorian Reform, the adoption of the Gregorian Calendar, the length of the tropical year and related matters.
Time and Dates
Information on date, time, and time zones from the New York Public Library.
Types of Calendars
An explanation of lunar, solar, lunisolar, rule-based and other types of calendars.
World Holidays: Weeks and Months
Information on the origin of the week, and etymology of month and weekday names.