Moon Phase Today

Why the moon has phases

The sun always lights half of the moon. As the moon circles Earth, we see that lit half from a changing angle: none of it at the new moon, when the moon sits roughly between us and the sun, all of it at the full moon, when it is on the far side of Earth, and part of it in between.^[7] A full cycle, from one new moon to the next, takes 29.53 days on average,^[6] but single cycles run anywhere from about 29.3 to 29.8 days because the sun's pull speeds the moon up and slows it down.^[5]

The four main phases (new moon, first quarter, full moon and last quarter) are single moments. Calendars, including the one above, give the whole local day of that moment the phase's name; on the days in between, the moon is a crescent or gibbous, waxing or waning.

Waxing or waning? How to tell from where you are

A waxing moon is growing toward full; a waning moon is shrinking toward new. Which side is lit depends on where on Earth you stand, because the moon looks rotated from different latitudes:

• Northern Hemisphere (US, Canada, UK, Europe, most of India): lit on the right means waxing, lit on the left means waning. An old memory aid: a waxing moon looks like the curve of a D, a waning one like a C.
• Southern Hemisphere (Australia, New Zealand, South Africa, Argentina): the other way round. Lit on the left is waxing, lit on the right is waning.
• Near the equator (Singapore, Nairobi, southern India): the crescent lies on its back like a boat, lit from below in the evening and from above before dawn.

There is a simpler test that works everywhere: a moon you see in the evening sky soon after sunset is waxing; one still up in the morning sky after sunrise is waning. The picture at the top of this page is turned the way the moon really looks from the city you choose, at the time shown under it.

Is the moon phase the same everywhere?

Yes. The phase depends only on where the moon is in its orbit, so at any given moment it is the same for everyone on Earth. Three things do change with your location: the local date and time of a phase (a full moon at 2 a.m. in London happens the evening before in New York), the way the moon is turned in the sky, and when it rises and sets. That's why the moon on your birthday depends on where you were born.

Why the moon rises later every day

While Earth turns once, the moon moves about a thirtieth of the way along its orbit in the same direction, so Earth has to turn a little extra before the moon comes back over the horizon. In New York over the next month, moonrise comes on average 52 minutes later each day, but the gap swings from 22 to 78 minutes, because the angle of the moon's path to the horizon keeps changing. In autumn the gap gets especially small around the full moon, which is why the Harvest Moon seems to rise at nearly the same time several evenings in a row.

Full moon names

Each month's full moon has a traditional name from North American folklore, such as the Wolf Moon in January and the Strawberry Moon in June. The full moon closest to the September equinox is the Harvest Moon, the one after it the Hunter's Moon, and a second full moon in the same calendar month is a Blue Moon.^[17] The next full moon, on November 24, is the Beaver Moon. These names follow Northern Hemisphere seasons, so they don't really fit in Australia or New Zealand.

How we calculate

Every number on this page is calculated for the exact coordinates of the place you choose: the phase and illumination from the positions of the sun and moon, moonrise and moonset when the moon's upper edge crosses a flat horizon, with the bending of light by the atmosphere included. Our phase times match the U.S. Naval Observatory's tables^[4] to within about a minute. The moon pictures are NASA's own renderings of the moon in each phase,^[50] turned to match your sky, and the place list comes from GeoNames.^[37]