A , or lunar calendar, is a timekeeping system based solely on the monthly cycles of the Moon's phases. While most of the modern world uses the solar-based Gregorian calendar, lunar calendars remain vital for tracking religious holidays, agricultural cycles, and cultural traditions. How a Moon Calendar Works

: These use "intercalary" or leap months to stay aligned with the solar seasons. The Chinese, Hebrew, and Hindu calendars are lunisolar, ensuring that seasonal festivals like the Lunar New Year or Passover always occur in the correct season. Modern Applications of the Moon Calendar

Depending on how they handle the discrepancy between the lunar and solar years, calendars fall into two main categories:

: These follow the moon strictly without adjusting for the sun. The Islamic (Hijri) calendar is a primary example; because it is shorter than the solar year, its months and holidays (like Ramadan) "drift" through different seasons over a 33-year cycle.

Beyond tracking holidays, many people use moon calendars today for practical and spiritual reasons: