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Moon Phases

See the Moon exactly as it is tonight, and when the next new and full moon arrive — converted to your time zone, not to UTC.

Today’s phase

Today’s phase

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— illuminated · — days

Next phases

  • New Moon—
  • First Quarter—
  • Full Moon—
  • Last Quarter—

How the phases work

The Moon makes no light of its own. Half of it is always lit by the Sun; what changes over the month is how much of that lit half we can see from here. When the Moon sits between us and the Sun, the lit side faces away and we see nothing — a new moon. When Earth sits in the middle, the lit side faces us fully — a full moon. Everything in between is a matter of angle.

That is why the phase is the same for everyone on the planet at a given instant, and why the same phase can carry two different dates on two different continents.

Tides

The Moon's gravity pulls the oceans into a bulge, and the Sun does the same with about half the strength. Around new and full moon the two line up and their effects add: high tides run higher and low tides lower. These are spring tides — from the sense of "springing up", nothing to do with the season. Around the quarters the Sun and Moon pull at right angles and partly cancel, giving neap tides, with the smallest range of the month.

So the dates above double as a rough tide calendar: the biggest tidal ranges cluster around the new and full moons, and the mildest around the quarters.

Where our months come from

The lunar cycle is the oldest unit of time humans kept after the day and the year. The wordmonth shares a root with moon, and the same pairing shows up across many languages. Twelve lunations come to roughly 354 days, about eleven short of a solar year, and every calendar in history has had to deal with that gap somehow.

The Islamic calendar keeps the lunar month and lets the year drift against the seasons, which is why Ramadan moves. The Hebrew and Chinese calendars insert a leap month every few years to stay aligned. The Roman calendar eventually cut the tie altogether, which is what we inherited — our months no longer track the Moon at all, and that mismatch is why a full moon can fall on any date.

Planting by the Moon

Agricultural calendars in many parts of the world assign tasks to lunar phases — sowing on one phase, pruning on another, harvesting on a third. In Brazil and across Latin America the practice is still widely followed, and a real body of traditional knowledge is attached to it.

We should be straight about the evidence, though: controlled trials have not found a reproducible effect of Moon phase on germination rates or crop yield. The tidal force the Moon exerts on the water inside a seed, a plant or a field is many orders of magnitude weaker than everyday effects — smaller than the pull of a truck passing on the road. What genuinely governs plant development is photoperiod, the length of the day, and that is the Sun.

None of which makes the tradition useless as a calendar. A rule like "sow on the waning moon" is a scheduling device: it spreads work evenly across the month and is easy to remember without anything written down. That is a real use. It just is not the Moon acting on the seed.

How these times are calculated

Phase times come from the method in chapter 49 of Jean Meeus's Astronomical Algorithms, which corrects the average cycle with periodic terms for the Sun's and Moon's positions and for the pull of the planets. The naive approach — take a known new moon and add 29.53 days repeatedly — drifts by several hours, which is enough to land on the wrong day in some time zone.

The results are checked against the US Naval Observatory and independently against published ephemerides: 204 phases spanning 1977 to 2027 agree to within two minutes, and the typical difference is under thirty seconds. The times you see are converted from Universal Time to your own zone by your browser.

Frequently asked questions

Is the Moon phase the same everywhere in the world?

Yes. The phase is the fraction of the Moon lit by the Sun, which is geometry between the Sun, Earth and Moon — so a full moon is a single instant shared by the whole planet. What changes is the local date and time: a full moon at 22:09 UTC falls on the 1st in London and on the 2nd in Tokyo. The times on this page are converted to your own time zone. The other difference is orientation: a crescent lit on the right in the northern hemisphere appears lit on the left in the southern one.

How long is a lunar cycle?

About 29.53 days from one new moon to the next — but that is an average. The real interval swings by around seven hours either way, because the Moon’s orbit is an ellipse and it moves faster when closer to Earth. This page computes each phase individually rather than adding a fixed number of days.

What is the Moon’s age?

The number of days since the last new moon. It runs from 0 to about 29.5 and then starts over. An age of about 15 days means a full moon.

Why are there sometimes two full moons in one month?

Because the cycle is 29.53 days and most months are longer. When a full moon lands in the first day or two of a long month, another one fits before the month ends. The second is popularly called a blue moon — nothing about its colour changes.

Do the Moon phases affect the tides?

Yes, and this one is real physics. Tides are raised by the gravity of the Moon and the Sun. At new and full moon the two pull in line and their effects add up, giving the largest range — spring tides. At the quarters they pull at right angles and partly cancel, giving the smallest — neap tides. So the strongest tides of the month arrive around the new and full moon listed above.

Do Moon phases affect planting, hair growth or the human body?

The planting tradition is genuinely old and widespread, but controlled studies have not found a reproducible effect of Moon phase on germination or yield. The tidal force the Moon exerts on the water in a field or a body is smaller than the one exerted by a truck driving past. What does drive plant growth is day length — that is the Sun, not the Moon. We list the traditional dates because people look for them, and we say plainly what the evidence shows.

How accurate are these times?

They are computed with the algorithm from chapter 49 of Jean Meeus’s Astronomical Algorithms, which is accurate to under a minute. We check the output against the US Naval Observatory and against published ephemerides — 204 phases between 1977 and 2027 agree to within two minutes, and most to within thirty seconds.

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