commons-suncalc 
A Java library for calculation of sun and moon positions and phases.
Features
- Lightweight, only requires Java 8 or higher, no other dependencies
- Android compatible, requires API level 26 (Android 8.0 "Oreo") or higher. For older Android versions, use commons-suncalc v2, which is similar to this version, but does not use the Java Date/Time API.
- Available at Maven Central
- Extensive unit tests
Accuracy
Astronomical calculations are far more complex than throwing a few numbers into an obscure formula and then getting a fully accurate result. There is always a tradeoff between accuracy and computing time.
This library has its focus on getting acceptable results at low cost, so it can also run on mobile devices, or devices with a low computing power. The results have an accuracy of about a minute, which should be good enough for common applications (like sunrise/sunset timers), but is probably not sufficient for astronomical purposes.
If you are looking for the highest possible accuracy, you are looking for a different library.
Quick Start
This library consists of a few models, all of them are invoked the same way:
ZonedDateTime dateTime = // date, time and timezone of calculation
double lat, lng = // geolocation
SunTimes times = SunTimes.compute()
.on(dateTime) // set a date
.at(lat, lng) // set a location
.execute(); // get the results
System.out.println("Sunrise: " + times.getRise());
System.out.println("Sunset: " + times.getSet());Read the online documentation for examples and API details.
See the migration guide for how to migrate from a previous version.
References
This library bases on:
- "Astronomy on the Personal Computer", 4th edition, by Oliver Montenbruck and Thomas Pfleger
- "Astronomical Algorithms" by Jean Meeus
Contribute
- Fork the Source code at GitHub. Feel free to send pull requests.
- Found a bug? Please file a bug report.
License
commons-suncalc is open source software. The source code is distributed under the terms of Apache License 2.0.