Prints
Moon calendar poster
Choose a year and, if you like, a time zone (your browser’s by default). The poster shows the Moon on every day of the year at 12:00 local time, with the days of the new and full moons marked.
What is on the poster
- Twelve columns, one for each month, and 31 rows for the days; each small Moon shows the phase at 12:00 local time in the chosen time zone.
- A solid gold ring marks the day of a full moon and a dashed ring the day of a new moon, by the local date in the chosen time zone.
How it is calculated
The phases come from the formulas in Jean Meeus’s Astronomical Algorithms, calculated in your browser. We check them against our own engine, which uses NASA’s JPL ephemeris: new and full moons agree to within three minutes.
Nothing leaves your browser
The year and the time zone you choose stay in your browser: the poster is calculated and drawn there, without any request to our server. We count only which kind of file was saved (for example “PDF, A4”), never the year or the time zone.
Sources
- Jean Meeus, Astronomical Algorithms (Willmann-Bell, 1991; second edition 1998): the formulas for the Sun and the Moon. en.wikipedia.org
- Park, R. S. et al., “The JPL Planetary and Lunar Ephemerides DE440 and DE441”, The Astronomical Journal 161, 105 (2021): the ephemeris of our own engine, used to check the formulas. doi.org
- Brandon Rhodes, Skyfield (MIT licence): the program of our own engine. rhodesmill.org
This page was written from the sources above. Where they disagree, we say so; claims we could not confirm are left out.