Next Full Moon

Why the date moves

Why is the full moon on a different date every month?

A full moon happens when the moon is exactly opposite the sun, and the moon takes 29.5 days to come around again — so each full moon lands about eleven days later in the Gregorian calendar than the last. Over a year that adds up to roughly eleven full moon dates worth of drift: the lunar year is 354.37 days, eleven days short of the solar year. The consequence is that the full moons of 2027 fall about eleven days earlier in the calendar than the full moons of 2026. The learn pages go deeper on the geometry.

Can a month have two full moons — or none?

Two, yes: when the drift is unlucky, one full moon lands near the start of a month and the next near the end, and the second is what the almanacs call a “blue moon”. None, only in February — it is the one month shorter than the 29.53-day lunar cycle, so a cycle can skip it entirely; the last time was 2018. The Snow Moon page has the details.

Why do different websites list different dates?

A full moon is an instant, and this site gives it in UTC. A site that rounds that instant to its own local calendar date will list a different day for any full moon near midnight UTC — a moon at 00:30 UTC is the 26th in London and still the 25th in New York. See themethodology for the convention this site uses.