Full moon in December 2029

The full moon of December 2029 falls on Thursday, 20 December 2029 at 17:47 EST, when the moon stands exactly opposite the sun. That night it rises at about sunset and sets at about sunrise, so it is above the horizon all night — and that is not a turn of phrase but the definition: the moon is full precisely when the earth lies between it and the sun, and we see the whole of the lit side.

On that day the moon is 398,110 kilometres from the earth. Its orbit is slightly elliptical, so the distance swings by some 40,000 kilometres over a month — at its closest the disc is about a seventh wider than at its furthest. You would only notice in two photographs side by side; the huge moon you sometimes see on the horizon is a trick of the eye and not an astronomical effect.

Two full moons are on average 29 days, 12 hours and 44 minutes apart. Because a calendar month is usually a little longer, the full moon drifts forward through the month, and roughly every two and a half years two of them land in the same one.