Lunisolar calendar

The Chinese, Buddhist, Burmese, Assyrian, Hebrew, Jain and Kurdish as well as the traditional Nepali, Hindu, Japanese, Korean, Mongolian, Tibetan, and Vietnamese calendars (in the East Asian Chinese cultural sphere), plus the ancient Hellenic, Coligny, and Babylonian calendars are all lunisolar.

Together with astronomical, horological, and phenological observations, definitions, measurements, and predictions of years, months, and days were refined.

Astronomical phenomena and calculations emphasized especially the efforts to mathematically correlate the solar and lunar cycles from the perspective of the earth,[citation needed] which however are known to require some degree of numeric approximation or compromise.

The traditional calendar used the sexagenary cycle-based ganzhi system's mathematically repeating cycles of Heavenly Stems and Earthly Branches.

[citation needed] The Gregorian calendar (the world's most commonly used) is a solar one but the Western Christian churches use a lunar-based algorithm to determine the date of Easter and consequent movable feasts.

[5] Intercalation of leap months is frequently controlled by the "epact", which is the difference between the lunar and solar years (approximately 11 days).

For instance, the Chehalis began their count of lunar months from the arrival of spawning chinook salmon (in Gregorian calendar October), and counted 10 months, leaving an uncounted period until the next chinook salmon run.