Moon phase calendar
New moons, quarters and full moons marked on the days they fall, on any month or year you like — printed alongside the ordinary calendar rather than instead of it.
How the dates are worked out
The phases are computed with the algorithms from Jean Meeus’s Astronomical Algorithms, the standard reference for this kind of calculation, including the Delta-T correction that accounts for the drift between Terrestrial Time and UTC.
That correction matters more than it sounds. Without it, a phase falling a minute either side of midnight lands on the wrong calendar day — and the error grows to several minutes by the end of the century.
Dates are given in UTC
A moon phase happens at one instant everywhere on Earth, but which calendar day that instant belongs to depends on where you are. A full moon at 23:30 UTC is still that day in London and already the next day in Berlin. The calendar uses UTC, which is the neutral choice; near midnight, check your own time zone before relying on the printed day.
What gets printed
- Month view — a small phase symbol in the corner of the day.
- Year view — a row under each mini-month listing the phase days.
- Week and day views — a larger symbol with the phase named in the calendar language.
Pick a year
The settings above stay as they are — only the year changes.