Calculate your Moon sign

The Moon's position comes from Astronomy Engine, computed to well under a degree of precision for the date and time you enter. Because the Moon moves roughly thirteen degrees a day, the main source of error is an uncertain birth time, not the calculation itself.

Leaving the birth time unknown checks whether the Moon changed sign at any point during that calendar day in your birthplace's zone. If it did, both signs are shown along with the changeover time, so you can see whether you need the exact hour to know which one applies to you.

A cusp Moon is a birth date where the Moon crosses into a new sign sometime that day, which happens roughly twelve times a month since the Moon moves so quickly. This is far more common than a cusp Sun sign, which happens only twice a year, which is why an exact time matters more for the Moon than for almost any other placement.

This calculator uses the tropical zodiac, the seasonal system most Western astrology is built on, where zero degrees Aries marks the spring equinox point rather than a fixed star. The sidereal zodiac, anchored to the visible constellations, would place the Moon in a different sign for some birth dates.

The birthplace sets the historical time zone for your birth date, which converts your entered local time into the correct astronomical instant before the Moon's position is calculated. Skipping it falls back to your device's current time zone, which is only correct if you were born in the same zone you are using this page from. For a birth before 1970 in a small set of zones — mostly the Low Countries, Scandinavia and the former Yugoslavia — the historical rules come from the tzdata backzone (release 2025c), compiled into the site.

No. The calculation runs entirely in your browser using a local astronomy library and an offline city list; nothing about your birth date, time or place is uploaded, stored on a server, or placed in the page URL.