How to use it
- Open the page: today’s phase, illumination and age are shown at once, with the next new moon, first quarter, full moon and last quarter.
- Pick any date between 1900 and 2100 to see the phase at local noon of that day and the phases that follow it.
- Browse the moon calendar month by month; click a day to select it. Days with a principal phase carry its name and time.
- Copy the summary or the link – times are shown in your time zone and in UTC.
Example
On 19 October 2026 the Moon is a waxing gibbous, about 9 days old and roughly 62% illuminated (the exact value depends on the time of day). The next full moon is on 26 October 2026 at 04:12 UTC (05:12 in Central Europe, 00:12 in New York), followed by the last quarter on 3 November and the new moon on 9 November 2026 at 07:02 UTC.
How the phases are calculated
The instants of the principal phases come from chapter 49 of Jean Meeus, Astronomical Algorithms(2nd ed., 1998). A lunation number k counts synodic months from the new moon of 6 January 2000; the mean phase time is a polynomial in k, and periodic corrections in the Sun’s mean anomaly M, the Moon’s mean anomaly M′, the argument of latitude F and the node Ω (25 terms per phase, plus 14 small planetary terms) give the true phase.
JDE = 2451550.09766 + 29.530588861·k + 0.00015437·T² − 0.000000150·T³ + 0.00000000073·T⁴ + Σ corrections
UTC = JDE − ΔT (ΔT ≈ 69 s in 2026, Espenak–Meeus polynomial)The result is in Terrestrial Time and is converted to UTC with ΔT. Checked against the U.S. Naval Observatory’s published phases, every new and full moon of 2025 and 2026 agrees to within 0.5 minutes; Meeus states the method is accurate to a few seconds for the current centuries, so published tables rounded to the minute may differ by one minute at most.
The illuminated fraction uses the phase angle from Meeus eq. 48.4, a short series in the mean elongation and anomalies (accuracy about 0.1°). Phase names follow the usual eight-phase scheme: the principal name on the local day the event occurs, otherwise waxing/waning crescent or gibbous by position in the lunation. The calendar discs show the phase at local noon, lit on the right while waxing as seen from the northern hemisphere.
Limits
Dates are limited to 1900–2100, where ΔT is well known. The small differences between “illumination 50%” and the quarter instants are real: quarters are defined by a 90° difference in ecliptic longitude, while the lit fraction also depends on the Moon’s latitude. Moonrise and moonset are not computed here.
Sources: Meeus, Astronomical Algorithms (1998), ch. 47–49, USNO – Phases of the Moon, NASA SVS – Moon phase and libration, Espenak & Meeus – Polynomial expressions for ΔT.
Questions
- When is the next full moon?
- The “Next phases” list shows the next full moon with its date and time in your zone and in UTC. After 26 October 2026 the following full moons are 24 November and 24 December 2026.
- Why does a moon app show a different percentage?
- Illumination changes by up to 12 percentage points a day around the quarters, so the time of day matters – this tool uses the current moment for today and local noon for other dates. Apps that round to the nearest phase picture can also differ by a day in the name.
- Is the moon phase different in Australia?
- No – the phase and the illuminated fraction are the same worldwide at the same instant. What changes is the clock time (a full moon at 04:12 UTC is the evening of the 25th in Los Angeles) and the orientation: south of the equator the lit side appears on the left while waxing.
- How accurate are the phase times?
- Within about one minute of the official USNO tables for the present decades. Over the full 1900–2100 range the uncertainty is a few minutes, mostly from ΔT (the irregular rotation of the Earth) being extrapolated into the future.