📅 Calendar Tools

The Lunar Calendar Explained

A lunar calendar tracks time based on the Moon's phases rather than the Earth's orbit around the Sun. The basic unit is the synodic month — approximately 29.53 days — which is the time from one new moon to the next. Twelve synodic months equal about 354 days, roughly 11 days shorter than the solar year of 365.25 days. This is why purely lunar calendars (like the Islamic Hijri calendar) drift through the seasons over years, while lunisolar calendars (like the Hebrew and Chinese calendars) add intercalary months to stay aligned with the solar year.

Moonrise and Moonset Times

Unlike the Sun, which rises roughly in the east and sets in the west each day, the Moon's rise and set times shift by about 50 minutes later each day. At new moon, the Moon rises and sets close to when the Sun does, making it invisible in the daytime glare. At first quarter, the Moon rises around noon and sets around midnight. At full moon, the Moon rises at sunset and sets at sunrise, providing maximum nighttime illumination. At last quarter, the Moon rises around midnight and sets around noon.

The exact times depend on your latitude and longitude. Near the Arctic and Antarctic circles, extreme seasonal variations in day length also affect when the Moon is above the horizon.

Moon Distance and the Elliptical Orbit

The Moon's orbit around Earth is elliptical, not circular. At perigee (closest approach), the Moon is approximately 356,500 km from Earth. At apogee (farthest point), it is approximately 406,700 km away — a difference of about 14%. This variation affects the Moon's apparent size and gravitational pull. When a full moon coincides with perigee, it appears roughly 14% larger and 30% brighter than a full moon at apogee — this is called a supermoon. The Moon's distance also affects tidal strength: perigee full and new moons produce especially strong "spring tides."

Lunar Months and Cultural Calendars

Across human history, the Moon has served as a natural timekeeping device. The word "month" derives from "moon." Many cultural and religious observances are tied to the lunar calendar: Ramadan begins at the new moon, Easter is calculated relative to the first full moon after the spring equinox, and the Chinese New Year falls on the new moon between January 21 and February 20. Knowing how many lunar months separate two dates is useful for tracking these traditional cycles.