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.
Astronomical Time Keeping Extensive descriptions of many astronomical time keeping systems, with information on time zones and Julian day numbers.
Time and Date Lots of time and date related information, such as yearly and monthly calendars, counters, countdown, and the world clock which shows the current time in cities all over the world.
Time and Dates Information on date, time, and time zones from the New York Public Library.
Blue Moon Myths Second full moon in a month, or third full moon in a single season?
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. The Maya Calendar website is developing with the intent of providing a complete view of Maya culture.
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 C functions for date conversion; plus software for calendrical conversion.
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.
The Chinese Calendar The mathematics of the Chinese calendar. Explains the rules for the Chinese calendar.
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.
Astro Portal - CalSKY The worldwide interactive online astronomical/space calendar and calculator - for friends of astronomy, as well as astronomers.
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. Christian, Pagan, Islamic, Hindu, and Jewish holidays.
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.
Julian Day Numbers An explanation of the Julian day number system used by astronomers and calendricists.
Types of Calendars An explanation of lunar, solar, lunisolar, rule-based and other types of calendars.
