Moon Phase Calculator - Phase for Any Date

About the Moon Phase Calculator

The Moon's changing shape has marked time for thousands of years. Many calendars — including the Islamic, Hebrew and Chinese calendars — are based on it, and festivals such as Easter, Ramadan, Eid, Passover, Diwali and the Lunar New Year depend on its phases. Gardeners, anglers, photographers, stargazers and night walkers all watch the Moon, and eclipses can only happen at new or full moon.

This moon phase calculator gives the Moon's phase, age in days and approximate illumination for any date, together with the exact times of the next four principal phases — new moon, first quarter, full moon and last quarter — in the time zone you choose. The phase times come from Jean Meeus' astronomical algorithm and are accurate to within a few minutes.

How to Use the Moon Phase Calculator

Enter a date.

Choose the time zone for the phase times.

The phase appears immediately, with the upcoming phases.

The Phases of the Moon

  New moon         the Moon is between Earth and Sun; the side facing us is dark
  Waxing crescent  a thin sliver, growing
  First quarter    half lit, about 7.4 days after new moon
  Waxing gibbous   more than half lit, growing
  Full moon        fully lit, opposite the Sun, about 14.8 days after new moon
  Waning gibbous   more than half lit, shrinking
  Last quarter     half lit, about 22.1 days after new moon
  Waning crescent  a thin sliver, shrinking toward the next new moon

A "quarter" moon looks half lit: the name refers to the Moon being a quarter of the way round its orbit, not to a quarter of the disc being lit.

How the Phase Is Calculated

  1. Find the most recent new moon before the date
     (Meeus: mean lunation plus periodic corrections for the
      Sun's and Moon's positions)
  2. Age = time since that new moon
  3. Illumination ≈ (1 − cos(2π × age ÷ lunar month)) ÷ 2
  4. Phase name from the age as a fraction of the month

Step-by-Step Example

29 September 2026 (at noon UTC).

  Previous new moon:   11 September 2026, 03:27 UTC
  Age:                 18.4 days
  Phase:               waning gibbous, about 86% lit
  Next last quarter:   3 October 2026, 13:25 UTC
  Next new moon:       10 October 2026, 15:50 UTC

A check against a famous event: the calculator places the new moon of 8 April 2024 at about 18:21 UTC, the time of that day's total solar eclipse across North America.

The Lunar Month

The time from one new moon to the next — the synodic month — averages 29.53 days, but individual months range from about 29.3 to 29.8 days because the Moon's orbit is elliptical and is tugged by the Sun. That is why the calculator finds each phase individually rather than simply adding 29.53 days. Twelve lunar months make about 354 days, 11 days short of a solar year, which is why lunar calendars drift through the seasons and why festivals such as Ramadan move earlier each year.

Full Moon Names

Many traditions name each month's full moon. In North American folklore, the full moons include the Wolf Moon (January), Snow Moon (February), Pink Moon (April), Strawberry Moon (June), Harvest Moon (the full moon nearest the September equinox) and Hunter's Moon (the one after). A blue moon is a second full moon in a calendar month, or the third of four full moons in a season. A supermoon is a full moon near the Moon's closest approach to Earth, when it looks slightly larger and brighter.

Moonrise and Visibility

The phase also tells you when the Moon is in the sky. A new moon rises and sets with the Sun, so it is lost in the daylight. A first quarter moon rises around midday and is high in the evening sky. A full moon rises around sunset and stays up all night, setting around sunrise. A last quarter moon rises around midnight and is best seen in the early morning. So for dark skies to see faint stars and the Milky Way, astronomers plan around the new moon; for moonlit walks or photographs of the lunar surface, the days around first quarter show the most detail along the shadow line.

Tides and the Moon

The Moon's gravity raises the ocean tides. When the Sun, Earth and Moon line up — at new moon and full moon — their pulls combine to give spring tides, with the highest high tides and lowest low tides. At the quarter moons the Sun and Moon pull at right angles, giving smaller neap tides. Anglers, sailors and coastal walkers therefore watch the phase as well as the local tide tables.

Same Phase, Everywhere

At any instant the Moon's phase is the same for everyone on Earth, but the local date and time of, say, a full moon depend on the time zone. The full moon of 17 October 2024 was at 11:26 UTC, which was 16:26 in Pakistan and 07:26 in New York. In the southern hemisphere the Moon appears upside down relative to the northern view, so a waxing crescent is lit on the left rather than the right.

Understanding Your Result

The headline gives the phase name.

The illumination line gives the approximate share of the disc that is lit and whether it is waxing or waning.

The Moon's age line gives the days since the last new moon and when it was.

The next phases line gives the next four principal phases with their times.

The time zone line confirms the zone used.

When Should You Use This Calculator?

Use it to plan stargazing, night photography or walks.

Use it to find the next full moon or new moon.

Use it to check the phase on a past date, such as a birthday.

Use it to understand lunar calendars and moon-based festivals.

Common Mistakes

Expecting a quarter moon to be a quarter lit. It is half lit.

Assuming every lunar month is 29.5 days exactly. Months vary by hours.

Forgetting time zones. A full moon late on one day in Europe is the next day in Asia.

Treating illumination as exact. It is a close approximation from the Moon's age, within a few percent.