How to use
- Pick a year and month. Your own time zone is used by default; you can switch to a city.
- Each day shows the moon's shape and illumination; the four main phases are marked with their exact time.
- Switch to Whole year for a table of every lunation, one row per lunar month.
- To get reminders, download the calendar file and import it into your calendar app.
Options explained
- Illumination
- The share of the moon's disc lit by the sun, calculated for midday; 0% is new moon and 100% is full moon.
- Southern hemisphere view
- The moon looks mirrored left to right from the southern hemisphere. Ticking it flips the pictures; it is ticked automatically when your time zone is in the southern hemisphere.
- Blue moon
- The second full moon in a single calendar month, judged by dates in the chosen time zone.
How the moon’s phases work
The moon has no light of its own; we see the half lit by the sun. As it orbits the Earth, the angle between sun, Earth and moon changes, so the lit part we see grows and shrinks over a synodic month of about 29.53 days on average.
| Phase | Days after new moon (approx.) | When to see it |
|---|---|---|
| New moon | 0 | Rises and sets with the sun, not visible |
| Waxing crescent | 2–5 | Low in the west after sunset |
| First quarter | about 7 | Rises around noon, high in the evening, lit on the right |
| Full moon | about 15 | Rises at sunset and is up all night |
| Last quarter | about 22 | Rises around midnight, high at dawn, lit on the left |
| Waning crescent | 24–27 | Low in the east before sunrise |
Left and right refer to the northern hemisphere; in the southern hemisphere they are reversed.
Planning photos and stargazing
For photos of a rising full moon, go out at sunset on the day of the full moon or the day before, when there is still light on the landscape. For the Milky Way or meteor showers, pick the days around new moon, when the sky is darkest. For moonrise and moonset in a specific city, use the sunrise and sunset times tool.
Frequently asked questions
How accurate are the times?
The new moon, quarter and full moon times use the algorithm in chapter 49 of Jean Meeus's Astronomical Algorithms, which normally agrees with published almanac times to within a minute. The daily moon pictures are illustrations based on illumination at midday.
Why does the full moon date change when I change the time zone?
A full moon happens at the same instant everywhere, but clocks differ. A full moon early in the morning in Beijing is still the previous afternoon in New York.
Why does the moon look full for more than one day?
Around full moon the illumination stays above 97% for about three days, so the moon looks full to the eye even though the exact full moon is a single moment.
Which years can I see?
Any year from 1900 to 2100.
Privacy
This tool runs entirely in your browser. Your files and text are processed on your device and are never uploaded to our servers.