Calendars & Time

Time

The official time source for the Department of Defense and the standard of time for the United States, this site also offers time zone information as well as sunrise and sunset calculations. See also the home page of the National Institute of Standards and Technology: Time and Frequency Division. For the really technical stuff on the earth's rotation and its effect on the measurement of time, see the International Earth Rotation Service (IERS).

Celestial

Important astronomical events, along with monthly star charts, are featured on this site for sky watchers. Included are sun and moon rise, transit, and set times as well as links to other WWW astronomy pages. See also Skywatching Center and Skycalendar.

This site provides a calculation tool for determining sun rise and set times, astronomical twilights, and moon rise and set times and phase for each night of the month.

For any year between 1900 and 2100, this site will generate a list of what constellation each planet is in for each month out of the specified year.

On this site you can obtain the times of sunrise, sunset, moonrise, moonset, transits of the sun and moon, and the beginning and end of civil twilight, along with information on the moon's phases (using a location or longitude/latitude designation).

Just as you would expect, this site provides complete and accurate data on solar and lunar events, eclipses, planetary positions, and other sidereal data.

This site can display an animation of the phases of the moon for any date and time during the years 1800 to 2199 A.D. See also Moon Phase.

Chinese

The 2011 Chinese calendar can be printed from this site, along with solar to lunar and lunar to solar conversions.

There are also useful links to other WWW sites on the Chinese lunar calendar.

Conversions

Convert dates among various calendar systems, including Julian, Gregorian, Jewish, and French republican.

Home page for the book by Nachum Dershowitz and Edward M. Reingold, Calendrical Calculations (1997). In addition to a large calendar converter, there are links to a variety of useful calendar WWW sites.

Holidays

Holidays affecting work schedules (federal holidays and observances, banking holidays) are calculated, along with other common holidays, from the late 18th century.

From 2000 to 2005, this site provides the principal holidays for many of the world's religions.

Just what the name says.

Islamic

This site provides the holidays for many of the world's religions, including Islam.

Jewish

From 2000 to 2005, this site provides the holidays for many of the world's religions, including Islam.

Generate a calendar of Jewish holidays for any year 0001-9999 and customize candle lighting times to your zip code, city, or latitude/longitude. See also The Jewish Calendar.

Roman

This site includes a program for calculating Easter Sunday in both the Western and Orthodox traditions. It also provide dates for other feasts in the Catholic calendar as well as other moveable feasts associated with Easter in the Western and Eastern traditions. There are references to both printed and online resources relevant to the dating of ecclesiastical events over time.

This site provides the holidays for many of the world's religions, including Christianity.

Just what the name says.