Track Moon Phases

The Moon orbits Earth approximately every 29.53 days, a period known as a synodic month. During this orbit, the angle between the Sun, Earth, and Moon changes continuously, causing the illuminated portion of the Moon visible from Earth to wax and wane. This cycle produces eight recognized phases: new moon, waxing crescent, first quarter, waxing gibbous, full moon, waning gibbous, last quarter, and waning crescent. Each phase lasts roughly 3.7 days, though the transition is gradual rather than abrupt.

Astronomical algorithms compute the Moon's ecliptic longitude relative to the Sun. When the difference is 0 degrees, it is a new moon; at 180 degrees, a full moon. The SunCalc library used by this tool implements these calculations with high precision, returning a phase value between 0 and 1 that maps directly to the eight named phases. The illuminated fraction is computed from the phase angle and accounts for the Moon's slightly elliptical orbit.

Moon phase information serves many disciplines. Astronomers plan observation sessions around new moons for the darkest skies. Photographers schedule landscape shoots during full moons for natural illumination and schedule astrophotography during new moons. Gardeners following biodynamic methods time their planting, pruning, and harvesting to specific lunar phases. Anglers use lunar calendars to predict peak feeding times. Even event planners and festival organizers sometimes align activities with full moons for atmospheric effect.

Each cell in the calendar grid shows three pieces of information: the day number, a moon phase emoji representing the current phase, and the illumination percentage. The emoji provides an instant visual cue, while the percentage gives a more precise reading. Today's date is highlighted for quick reference. Below the grid, summary cards display the current phase details and the dates of the next full moon and new moon, so you can plan ahead without scanning every day manually.