Moon Phase Calendar
Moon phase for any date with a month of mini icons, illumination percent, moon age and the next key phases.
How does the moon phase calendar work?
Pick any date and the tool renders that day's moon as a large canvas drawing with the terminator shaded in, shows the phase name, the illuminated percentage and the moon age, and browses a whole month of mini moon icons. It also lists the next eight key phases — new moon, first quarter, full moon and last quarter — with their exact local dates and times.
Why does the moon have phases at all?
The Moon does not produce light; we see it only by reflected sunlight. As it orbits Earth roughly once every 29.5 days, the sunlit half faces us at different angles: we see none of it at new moon, the whole disc at full moon, and a changing slice in between. Nothing blocks the Moon — only the viewing geometry changes.
How accurate are the phase dates and times?
The tool computes everything with the Astronomy Engine, a professional-grade ephemeris library: the new, quarter and full moon instants it lists are typically accurate to within a minute of official almanacs. Differences of a minute or two between sources come from slightly different physical models and time scales.
What does the illuminated percentage mean?
It is the fraction of the moon's visible disc that catches sunlight, from 0% at new moon to 100% at full moon. Around the quarters it passes 50%. The number changes by roughly 10 percentage points per day near the equinoxes of its orbit, which is why the moon looks noticeably different every evening.
What is the moon age shown under the drawing?
Moon age is the time since the last new moon, expressed in days. A full cycle averages 29.53 days, so an age near 0 or 29.5 means a dark new moon, about 7.4 days a first quarter, 14.8 days a full moon and 22.1 days a last quarter.
Can I find the date of the next full moon?
Yes — the Next 8 key phases panel lists the upcoming new moons, first and last quarters and full moons with the exact date and clock time in your local time zone. Click any entry to jump the calendar and the big view straight to that day.
Why do my mini icons sometimes look slightly different from photos of the same night?
The icons draw the geometric terminator of the phase. Real photos can look subtly different because of the moon's tilt in the sky, which shifts with your latitude and the time of night, plus libration that gently rocks the visible face. The percentage and age are unaffected.
Does the tool need my location or internet access?
No. Moon phases are the same for the whole Earth at any instant, so no location is needed, and all calculations run locally in your browser with the bundled Astronomy Engine — no network requests are made at all.
How to Use Moon Phase Calendar
This moon phase calendar renders any date's moon as a large canvas drawing with the terminator shaded, shows the phase name, illuminated percentage and moon age, browses a whole month of mini moon icons, and lists the next eight key phases (new moon, first quarter, full moon, last quarter) with exact local dates and times — all computed locally by the bundled Astronomy Engine.
- Pick a date with the date picker, the previous/next day arrows or the Today button; the big moon, phase name, illuminated percent and moon age update instantly.
- Browse the month grid below: every day carries a mini moon icon drawn from that day's real phase, with today outlined and your selected day ringed. Press the month arrows to move between months.
- Click any day in the grid to select it — the big view jumps there, which is handy for finding a full moon night before planning an observation or a photo session.
- Check the Next 8 key phases panel: it lists upcoming new moons, first and last quarters and full moons with the exact clock time in your time zone; clicking an entry jumps the calendar to that day.
- Switch your system or site theme between light and dark — every moon icon and the big drawing re-shade automatically to stay readable.
The illuminated percentage climbs roughly 10 points per day around the quarters, so if you want a dramatic crescent shoot, target dates two to four days from new moon listed in the key-phases panel.
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