The colophon
About The Moon Almanac
A small, fast reference for the Moon: tonight's phase, the month ahead, and the science of why the shape changes — computed, not copied.
Where the data comes from
Every phase, illumination percentage, moonrise, moonset and distance figure on this site is computed from lunar geometry using SunCalc, an open-source astronomy library implementing standard published formulas for the positions of the Sun and Moon. Nothing is scraped or copied from other almanacs — if you check a date here and in a printed ephemeris, they should agree.
How we verify it
Before every release, our build runs an automated check of the computed new-moon and full-moon instants against independently published reference dates. Principal phase times are typically accurate to within a few minutes — more than enough for knowing what the sky will do tonight. The one caution: this site is made for planning and wonder, not navigation — do not use it where precision timing is safety-critical.
A note on time zones
A full moon is a single instant that happens for the whole planet at once. We list those instants in UTC. If a full moon falls near midnight UTC, your local calendar may put it a day earlier or later — that is normal, and it is why two calendars can honestly disagree about "the date" of a full moon. Location-aware pages (like moonrise & moonset) use your device's location, computed entirely in your browser.
Privacy
The site is fully static. If you grant location access for the sky views, the calculation happens on your device; your position is never sent to a server. No accounts, no tracking pixels.
Start exploring
Begin with tonight's moon, browse the moon calendar, look up the moon on your birthday, or read why the Moon changes shape.