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Astronomical calendar systems

Solar calendar

A solar calendar is a calendar whose dates indicate the position of Earth on its revolution around the Sun or, equivalently, the apparent position of the sun moving on the celestial sphere.

Lunar calendar

A lunar calendar is a calendar that is based on cycles of the lunar phases. Because there are slightly more than twelve lunations (synodic months) in a solar year, the period of 12 lunar months (354.37 days) is sometimes referred to as a lunar year.

Lunisolar calendar

A lunisolar calendar is a calendar in many cultures whose date indicates both the moon phase and the time of the solar year.

If the solar year is defined as a tropical year, then a lunisolar calendar will give an indication of the season; if it is taken as a sidereal year, then the calendar will predict the constellation near which the full moon may occur.