kuuaasta

Kuuaasta, also known as the lunar year, is a calendar system based on the cycles of the Moon's phases. A lunar year typically consists of 12 lunar months, with each month beginning on the new moon. The duration of a lunar month is approximately 29.53 days, making a standard lunar year about 354.36 days long. This is roughly 11 days shorter than a solar year, which is based on the Earth's revolution around the Sun.

The difference between lunar and solar years means that purely lunar calendars do not stay aligned with the seasons. Over time, festivals and observances tied to a lunar calendar would drift through the solar year. To address this, many cultures have adopted lunisolar calendars, which incorporate adjustments to keep the lunar months roughly synchronized with the solar year and its seasons. These adjustments often involve adding an intercalary or leap month periodically.

Historically, various civilizations have utilized lunar or lunisolar calendars. Examples include the traditional Chinese calendar, the Islamic calendar (which is purely lunar), the Hebrew calendar, and the ancient Babylonian calendar. The concept of a "kuuaasta" emphasizes the moon's influence on timekeeping and its importance in cultural and religious practices for many societies throughout history.