Sonnenuntergang-Sonnenaufgang.de is an online solar and lunar calendar operated by Guido Gerding in Germany. It helps users find calculated sunrise, sunset, twilight, and moon data for locations around the world. Visitors can set their location automatically, search by city or postal code, or adjust a map marker. The calendar displays daily sunrise and sunset times, day length, and the Sun’s highest point, with options to view civil, nautical, or astronomical twilight and adjust the time zone.

The site also provides monthly moonrise and moonset times and lunar phases, including the percentage of illumination. Planning tools let users compare two locations and transfer a calendar time into a simple task planner. A local-time clock is available for a selected place, alongside settings, FAQs, and usage guidance. The service is designed to support activities such as photography, gardening, and general scientific planning. Its times are generated using astronomical algorithms and are presented with a disclaimer that conditions and local factors may cause differences; the data is not intended for safety-critical navigation.