SunCalc

SunCalc is a tiny dependency-free JavaScript library for calculating solar and lunar information for any location and time. It provides sun altitude and azimuth together with sunrise, sunset, twilight, and other sunlight phases. Moon calculations include position, rise and set times, distance, and illuminated phase. Version 2 rebuilt the astronomy around higher-order models from Jean Meeus and validates results against authoritative astronomical references. Typical rise and set errors are around 15 seconds, with substantially improved positional accuracy over the earlier release. It ships as a modern ES module while retaining bundled support for CommonJS and direct browser use.