lunisolärt

Lunisolar, or lunisolar, refers to calendars or timekeeping systems that integrate both lunar cycles and the solar year. In these systems, months are typically tied to the phases of the Moon, while the overall year is adjusted to stay in sync with the Sun and the seasons.

In practice, months usually begin with a New Moon or another significant lunar phase, and lunar months commonly alternate between 29 and 30 days to approximate the synodic month, which lasts about 29.53 days. To prevent drift of the calendar relative to the solar year, an intercalary or leap month is inserted periodically. The pattern for adding leap months varies by tradition and can follow different cycles, most notably the 19-year Metonic cycle that introduces seven leap months in that period.

Examples of lunisolar calendars include the Hebrew calendar, the traditional Chinese calendar, and various Hindu calendars. The Hebrew calendar uses leap months roughly every two to three years, while the Chinese calendar inserts a leap month when solar terms require adjustment. Hindu lunisolar calendars also employ intercalary months to keep festivals aligned with the agricultural and solar seasons.

Purpose and use: lunisolar calendars guide religious observances, agricultural activities, and cultural festivals in societies where both lunar visibility and solar seasons are important. They are distinct from purely lunar calendars, which do not seek solar alignment, and from solar calendars, which do not rely on lunar months.