Astronomical Information Center
Terms used on this website
Phenomena of the Sun and Moon
- Rise, Set, and Twilight Definitions
- Comparative Lengths of Days and Nights
- Length of Day and Night at the Equinoxes
- Sunrise and Sunset Times Near the Solstices
- Visibility of the Crescent Moon
- References on Eclipses
- Phases of the Moon and Percent of the Moon Illuminated
Time
- Universal Time
- Terrestrial Time
- Approximate Sidereal Time
- U.S. Time Zones
- World Time Zone Map
- Daylight Saving Time
- The Equation of Time
Calendars and Historical Events
- Introduction to Calendars
- Leap Years
- U.S. Holidays
- The International Date Line
- The 21st Century and the 3rd Millennium
- The First Sunrise of the New Year
Computing Astronomical Data and Phenomena
- Converting Between Julian Dates and Gregorian Calendar Dates
- Computing Times of Rise, Set, and Twilight
- Computing Approximate Solar Coordinates
- Computing Approximate Sidereal Time
- Computing Altitude and Azimuth