Nachtbeginn

Nachtbeginn is a German term meaning the onset of night. Der Begriff setzt sich aus den Wörtern Nacht und Beginn zusammen. In everyday usage it refers to the transition from daylight to night, typically occurring after sunset when the sky darkens.

In astronomy, Nachtbeginn describes the start of astronomical night, defined as the moment when the Sun is 18 degrees below the horizon. At that point, the sky is dark enough for most astronomical observations. The boundary between day and night varies with latitude and season, so the exact time of Nachtbeginn can differ widely. Civil twilight and nautical twilight precede the onset of Nachtbeginn, and the duration of twilight depends on latitude, season, and atmospheric conditions.

In everyday life, Nachtbeginn is also used in a more colloquial sense to denote the start of night hours for social, cultural or regulatory purposes. Many German-speaking jurisdictions use the concept to define the beginning of Nachtzeit or Nachtruhe, with implications for noise restrictions, licensing hours and public conduct.

See also: Dämmerung, Nacht, Nachtzeit, Nachtruhe.