Moon Phase Calendar — Tonight, This Month, and Beyond
See the moon as it looks tonight, scan the whole month at a glance, and find the next full or new moon down to the minute. All computation runs locally in your browser — no sign-up, no API key, no tracking.
The Moon Phase Calendar is a four-in-one lunar tool. The hero panel shows tonight's moon with its phase name, illumination percentage, and age in days — plus the next new, first-quarter, full, and last-quarter moons in short form. A date picker lets you check any day from year 1900 onward to within one minute of accuracy. A monthly calendar grid shows every day of the month with a miniature SVG moon and illumination percentage, navigable with the ‹ • › arrows. And a chronological table lists the next 12 major phases — roughly three lunar cycles ahead — with the exact date, local time, and days-from-now for each. A Northern / Southern hemisphere toggleflips the moon's orientation if you observe from below the equator.
On Monday, May 11, 2026 the moon is a Waning Crescent with 32.0% of its face illuminated, 23.9 days into the synodic month (which lasts 29.5 days from new to new). Pick any past or future date above — the calculation works to within a minute back to year 1900 and forward beyond 2100.
| Phase | Date | Time (your local) | Days from now |
|---|
How the moon cycle works
The moon takes about 29 days, 12 hours, and 44 minutes — a synodic month — to complete one cycle from new moon to new moon. During that time it traces a roughly elliptical orbit around Earth while the Earth-moon system together orbits the Sun. From our vantage point on the surface, the changing relative angles between Sun, Earth, and Moon make the lit half of the moon appear to grow and shrink — first as a thin crescent on one side, then a half-disc, then a fat gibbous shape, then full, then back down through the gibbous, quarter, and crescent stages on the other side.
The illumination is always half — the moon, like any sphere lit from one direction, is exactly 50% lit at any instant. What changes is the part of that lit half we can see from Earth. At new moon the lit half faces directly away from us; at full moon it faces directly toward us; at the quarter phases we see half of the lit half (a quarter of the total surface).
The eight traditional phases
The four "quarter" phases (new, first quarter, full, last quarter) are the exact astronomical events used throughout this tool. The four "in-between" names (waxing / waning crescent / gibbous) refer to the rest of the cycle.
| Phase | Illumination | What it looks like and what it means |
|---|---|---|
| New Moon | 0% | Moon between Sun and Earth — dark side faces us. The sky is at its darkest; best for stargazing and Milky Way photography. |
| Waxing Crescent | 1–49% | A thin lit sliver grows on the right (Northern view). The moon sets a few hours after the Sun, visible in the evening sky. |
| First Quarter | ~50% | Right half of the disc is lit (Northern view). The moon rises around noon and sets around midnight — great for daytime visibility. |
| Waxing Gibbous | 51–99% | Most of the disc is lit and growing. The moon dominates the evening sky and stays up most of the night. |
| Full Moon | 100% | Moon opposite the Sun in our sky. Rises at sunset, sets at sunrise, dominates the entire night. Highest tides of the month. |
| Waning Gibbous | 99–51% | Most of the disc is lit but shrinking. The moon rises a few hours after sunset and is high overhead before dawn. |
| Last Quarter | ~50% | Left half is lit (Northern view). The moon rises around midnight and is high in the south at sunrise. |
| Waning Crescent | 49–1% | A thin lit sliver on the left, shrinking. Visible only in the pre-dawn eastern sky. The "old moon". |
How to use the calendar
- Read tonight’s phase from the hero. The top card shows the moon as it appears right now, with its phase name (e.g. Waxing Gibbous), the percent of its face that is illuminated, and how many days have passed since the most recent new moon. The four "next" rows tell you when the upcoming new, first-quarter, full, and last-quarter moons fall.
- Switch hemisphere if you are south of the equator. Northern and southern observers see the moon’s lit limb on opposite sides. Use the Northern / Southern toggle to flip the orientation — the math is the same, only the picture flips. Default is Northern; pick Southern if you’re in Australia, Argentina, South Africa, New Zealand, etc.
- Pick any date to see its phase. The date picker accepts any day. The card directly below it shows the moon as it appeared (or will appear) on that date — phase name, illumination, and moon age. The calendar grid jumps to that month so you can scan the whole lunation around the date.
- Click days in the calendar grid. Every day has a mini-moon icon and an illumination percentage. Click any cell to select it (the cell turns green); use the ‹ • › buttons to step months. Days outside the current month are dimmed but still clickable.
- Read the next-12-phases table. Underneath the calendar, a chronological table lists the next twelve major phases (roughly three lunar cycles ahead). Each row gives the phase name, the date and time in your local time zone, and how many days from now the phase falls. Useful for planning night photography, dark-sky stargazing, or full-moon hikes.
What people use the Moon Phase Calendar for
Six recurring patterns from the analytics of similar lunar-calendar tools.
Planning night photography around the new moon
Astrophotographers, Milky Way shooters, and meteor-shower watchers want the moon out of the sky — or at least a thin crescent. The Moon Phase Calendar shows the next new moon at a glance, and the calendar grid lets you scan the surrounding nights to see which evenings still have less than 10% illumination. Aim for a 3–5-day window centred on the new moon.
Picking the next full moon for a hike or beach walk
Full-moon hikes are a tradition — bright enough to walk without a headlamp, low-angle light on the landscape. The Next 12 Phases table tells you exactly when the next full moon falls, in your local time. The full moon also produces the highest tides of the month, useful for tide-pool walks and coastal photography.
Cross-checking traditional moon-based dates
Ramadan begins at the sighting of the new crescent moon. Easter is the first Sunday after the first full moon on or after the spring equinox. Passover begins at sunset on the 15th day of Nisan — a full moon. The calendar lets you confirm exactly when the relevant new or full moon falls in any year past or future.
Gardening by the moon (biodynamic / lunar calendar)
Lunar-calendar gardening traditions plant root crops in the waning moon and above-ground crops in the waxing. Whether or not the practice has measurable yield benefits, many growers swear by it — and this tool gives an unambiguous answer to "is the moon waxing or waning this week?".
Astronomy education and homework
Students often need the moon phase for a specific date — a birthday, a historical event, a teaching schedule. The date picker handles any year from 1900 onward (and well beyond 2100) with one-minute precision. The calendar grid is also a great visual aid for showing how a full lunation builds from new to full to new again.
Tide and fishing planning
Spring tides (the largest tidal swings) happen near new and full moons, when the Sun, Earth, and Moon align. Neap tides (smallest swings) happen near the quarters. Anglers and surfers use the phase table to plan trips around the biggest tidal pulls of the month.
Astronomical constants used
Every value displayed in the calendar derives from a small set of astronomical constants and formulae. The numbers below are the basis of every phase, date, and illumination shown.
| Quantity | Value | Source |
|---|---|---|
| Synodic month (new to new) | 29 days 12 h 44 min (29.5306 days) | IAU mean value |
| Sidereal month (relative to stars) | 27 days 7 h 43 min (27.3217 days) | IAU mean value |
| Average Earth–Moon distance | 384,400 km / 238,855 mi | NASA / IAU |
| Moon mean radius | 1,737.4 km / 1,079.6 mi | NASA Lunar Fact Sheet |
| Mean orbital speed | 1.022 km/s (~3,680 km/h) | NASA |
| Tilt of moon’s orbit to ecliptic | 5.145° | IAU |
| Apparent angular size from Earth | ~0.5° (similar to the Sun) | Observed |
| Full lunation phase formula | fraction = (1 − cos(2π · phase)) / 2 | Meeus, Astronomical Algorithms |
Why the moon flips between hemispheres
The moon’s lit limb is on the right when waxing (and on the left when waning) — for an observer in the Northern Hemisphere. Cross the equator and the picture flips: Southern observers see the lit limb on the opposite side at every phase. The reason is purely geometric: a Southern observer is, in effect, "upside down" relative to a Northern one, so the same physical lighting on the moon looks rotated 180°. Near the equator the terminator (the day-night line on the moon) appears almost horizontal, producing the "wet-moon" smile shape. Use the toggle in the tool above to flip the orientation; the math behind the phase is identical worldwide — only the picture rotates.
Related lunar and solar tools
For the moon's position in the sky from a specific location (azimuth, altitude, moonrise, moonset, sublunar point): Moon Position Map. For the live day/night terminator showing where the Sun is currently up: Day Night Map. For sunrise, sunset, and twilight at any location and date: Sunrise & Sunset Calculator. For the Sun's position at a specific time (solar azimuth, elevation, shadow direction): Sun Position Calculator. To compare clock times across multiple cities: Time Difference Calculator.
Frequently asked questions
Phase math: SunCalc (BSD-licensed), implementing the algorithms of Jean Meeus, Astronomical Algorithms (2nd ed., 1998). The library computes the geocentric ecliptic longitude of the Sun and Moon to derive the phase angle. The illuminated fraction is (1 − cos(phase angle)) / 2; the synodic phase value is the angular position along the cycle from new (0) through full (0.5) and back to new (1). Moon constants (radius, mean distance, sidereal and synodic month lengths): NASA Lunar Fact Sheet and IAU recommended values. Next-phase times are computed by a one-minute bisection over the phase-angle function. SVG moon rendering uses the standard arc-plus-ellipse approach — a half-disc bordered by an elliptical terminator whose horizontal axis equals R · |cos(2π · phase)|. All computation runs locally in your browser — no network calls.
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