Why moonrise shifts about 50 minutes a day
The Moon keeps a schedule that drifts against the clock. On average it rises about 50 minutes later each day, and over a month those delays wrap all the way around the dial. The reason is that Earth and the Moon are moving at once. The Moon takes 27.3 days to complete one orbit, but while it does, Earth keeps turning on its axis. By the time the Moon returns to the same celestial position, Earth has rotated an extra 13.2° eastward to catch up to it — and 13.2° of rotation takes about 53 minutes. So the Moon comes up later, night after night.
That 50-minute figure is an average, not a rule, and the real lag swings from roughly 20 to 80 minutes because the Moon's orbit is tilted 5.1° to the ecliptic and is slightly elliptical. The table below shows six consecutive moonrises in New York in late September 2027, where the lag stretches from 50 minutes to nearly 80 across a single week — a good reminder that the average hides a lot of variation.
| Date (New York, 2027) | Moonrise | Later than the day before |
|---|---|---|
| Sep 20 | 20:02 | — |
| Sep 21 | 20:52 | 50 min |
| Sep 22 | 21:52 | 60 min |
| Sep 23 | 23:01 | 69 min |
| Sep 24 | 00:17 | 76 min |
| Sep 25 | 01:36 | 79 min |
Moonrise times computed for New York (40.71°N, 74.01°W) on the stated dates, local clock time.
Synodic and sidereal months are different clocks
Two month-lengths appear in every moon calculation, and confusing them gives wrong answers.
| Month | Length | What it measures |
|---|---|---|
| Synodic month | 29.53 days | New moon to new moon — the phase cycle |
| Sidereal month | 27.32 days | One orbit measured against the fixed stars |
The gap of about 2.2 days is not an error; it is Earth's own motion. While the Moon completes one orbit of Earth, Earth has moved about one-thirteenth of the way around the Sun, so the Moon needs roughly two extra days to line back up with the Sun and be "new" again. The synodic month is the one that governs phases and ages; the sidereal month governs where the Moon sits among the stars. Moonrise times depend on both, because the Moon's position in the sky changes from both its orbital motion and the tilt of your horizon.
Why some days have no moonrise or no moonset
Because the Moon rises about 50 minutes later each day, its rise and set times slide past midnight at predictable points each month. On the day a event happens to fall just after midnight, the previous day may have no such event at all — the Moon was already up when the day began and still up when it ended. The effect is strongest at high latitudes, where the lag between successive events can be larger.
London (51.5°N) in 2027 is a clear example. There are around a dozen dates that year with no moonrise at all, and a similar number with no moonset. On 15 June 2027, for instance, the Moon is 89% illuminated and simply does not rise during the calendar day — it climbed above the horizon late the previous evening and does not set until 01:06 the next morning. The calculator above reports "—" for such days rather than inventing a time.
The Moon swings along the eastern horizon
Moonrise does not occur at the same point of the compass every night. As the Moon moves around its orbit its declination changes, and that shifts the azimuth of moonrise back and forth along the horizon by tens of degrees over a month — the same seasonal swing the Sun makes over a year, but compressed into four weeks. The Moon also reaches extremes the Sun never does: its orbit is tilted 5.1° to the ecliptic, so its maximum and minimum declinations are about 5° beyond the Sun's, which is exactly why the Moon can rise as far north-east in summer, or south-east in winter, as it does.
Full moons rise at sunset; new moons travel with the Sun
The phase of the Moon and the time it rises are locked together, and knowing the link lets you estimate the phase with no tool at all. At full moon the Moon is opposite the Sun, so it rises in the east just as the Sun sets in the west, stands highest around midnight, and sets at sunrise. At new moon it is beside the Sun in the sky, rising and setting with it and lost in the glare. In between, first quarter rises near noon and sets near midnight, while last quarter rises near midnight and sets around noon. On 15 September 2027, a full moon, New York sees moonrise at 17:41 against a sunset of 18:07 — the pattern in a single line.
Three worked examples
Example 1 — a full moon rising at sunset. On 15 September 2027 the Moon is full and rises at 17:41 in New York, 17:31 in London and 17:12 in Tokyo, each a few minutes before that city's sunset (18:07, 18:18 and 17:51). Full moons are therefore up all night, which is why they are the worst nights for meteor watching and the best for photographing a landscape by moonlight.
Example 2 — a day with no moonrise. In London on 15 June 2027 the Moon does not rise at all. It is 89% illuminated and stays above the horizon from the previous evening until it sets at 01:06, so the calendar day contains a moonset but no moonrise. The calculator shows "—" for the missing event.
Example 3 — a moonless, dark night. In New York on 2 August 2027 the Moon is new — 0% illuminated — and rises at 06:15 and sets at 19:29, leaving the whole night dark. That is the night to plan a deep-sky session or a meteor watch, and it is the mirror image of Example 1.
How these times are computed
The times above are not read from a printed table; they are calculated in your browser from the Moon's position. The method finds the instants when the Moon crosses your local horizon, accounting for its motion along its orbit, its varying distance and your latitude and longitude. A rise or set is defined as the moment the upper limb of the Moon touches the horizon, which is why the result can differ by a minute or two from a source that measures the Moon's centre instead. Local horizon features — a hill, a building, a treeline — are not included, so treat the figures as the times for a flat, sea-level horizon at your coordinates.
Two further details explain most of the remaining small discrepancies. The Moon's apparent position is shifted slightly by parallax, because you are standing on Earth's surface rather than at its centre, and that shift is larger for the Moon than for any other body simply because it is so close. And the Moon is not a point: its disc spans about half a degree, so the light of the rising limb arrives a little before the centre crests the horizon. Both effects are small but real, and both are why a calculator can disagree with a planetarium app by a minute or so without either being wrong.
Watching a moonrise or a moonset
Moonrise moves along the horizon and slides about fifty minutes a day, so what you need is the bearing and something to look through. These are the items for following the Moon this page tracks.
- Compass — Moonrise clips the horizon tens of degrees either side of east over a month. A compass tells you which patch of sky to watch tonight.
- 10x50 binoculars — Along the terminator the craters and mare stand out in relief, and a low-power binocular shows more of the Moon at once than a small telescope can frame.
- Moon filter — A near-full Moon is uncomfortably bright through optics. A neutral moon filter cuts the glare without the colour cast of sunglasses.
- Planisphere — The rise time is only part of the picture; a star wheel shows where the Moon sits against the constellations on the same night.
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Sources and standards
Where these figures come from
Every formula on this page is implemented from the published reference material below. Where a value depends on a regional code, the calculator lets you override it rather than assuming one jurisdiction.
- NASA Science — Moon — lunar phases, libration and the orbital mechanics behind the position used for rise and set.
- NASA Science — Moon phases — the synodic month and the eight named phases referenced on this page.
- NOAA Global Monitoring Laboratory — solar and local time calculations used to place moonrise on your calendar day.
Figures, formulas and reference tables last verified: 24 September 2026.