Please see Astronomical Data Used for Litigation if you are interested in using the data produced by this service for legal purposes.
DefinitionsFor more information on the terms used, see the Astronomical Almanac Glossary , or the Rise, Set, Transit, and Twilight Definitions, and the Phases of the Moon and Percent of the Moon Illuminated pages in the Astronomical Information Center.
Computing Data for Multiple DaysIf you need rise, set, or twilight times for a series of dates for a specific location, use our
Sun or Moon Rise/Set Table for One Year service, which computes a one-page table covering a calendar year Rise/Set/Transit Times for Major Solar System Bodies and Bright Stars service, which computes Sun/Moon/planet/star phenomena for a given number of days Lunar InformationThe moon phase and fraction illuminated provided are computed for noon on the date requested, in the time zone requested.
Time FormatsAll the output times will be on a 24-hour clock.
Time ZonesWhen using the "Need USA Location" button, the service will fill the Time Zone hours field and set the Time Zone direction button according to the current standard time zone of the US place entered.
The railroads introduced standardized time zones to the USA in 1883. Since then, time zone boundaries he evolved considerably, with many cities and counties shifting from one zone to another. This service makes no attempt to track such historical changes.
For locations that require it, you may enter the time zone in decimal hours. For example, for locations in India, you may enter 5.5 hours east of Greenwich for the time zone. The time zone field can accommodate up to five characters.
Daylight Sing TimeThis service implements US daylight sing time (DST) rules for dates from 1967 through the present day in accordance with the Uniform Time Act of 1966 and subsequent legislation. If you set the "Account for US Daylight Sing Time" radio button on, the results will include a 1 hour offset to the given Time Zone hour if the requested date occurs during a DST period.
This service does not evaluate whether a location associated with manually entered coordinates observes DST. When using the "Need a USA Location" button, the service will set the "Account for US Daylight Sing Time" radio button according to the current practice in that location. For instance, most locations in Arizona do not observe Daylight Sing Time, and therefore the "No" radio button will be automatically selected.
Application Programming InterfaceThis data service uses one of our Application Programming Interfaces (APIs). The API returns data in JaScript Object Notation (JSON) format for users who wish to manipulate data into a customized format. For more information on the API, please see the documentation page.
Sunset photo by Lu Rarogiewicz from Mt. Wilson, California.