From Wikipedia, the free encyclopedia
A lunar calendar is a calendar in many cultures that is oriented at the moon phase.
This is normally done by having a month which corresponds to a lunation so that the day of month indicates the moon phase. If a calendar tracks the seasons, it is also a lunisolar calendar.
Since there are about twelve lunations (synodic months) in a solar year, this period (354.37 days) is sometimes referred to as lunar year, corresponding to thirteen sidereal months (355.18 days).
Most lunar calendars are also lunisolar, such as the Chinese calendar, Hebrew calendar, and Hindu calendar, and most calendar systems used in antiquity. The reason for this is that a year is not evenly divisible by an exact number of lunations, so without any correction the calendar year will drift with respect to the seasons. The only widely used purely lunar calendar is the Islamic calendar, whose year always consists of 12 lunations. As a result of this, it is mostly used for religious purposes, alongside a secular solar calendar, and Islamic celebrations perform a full circle with respect to the seasons every 33 years.