Moon phase settings
Moon Phase Clock
See the current moon phase, illumination, moon age, and upcoming major phase in a live display.
Lunar-cycle estimate
This page uses a fixed mean lunar cycle. It starts from a reference new moon at 2000-01-06 18:14 UTC and divides elapsed time by a mean synodic month of 29.530588853 days. The cycle fraction sets the phase label, estimated age, and the next quarter-cycle boundary. Illumination uses a cosine phase model.
Example: at one quarter of the model cycle, age is about 7.4 days, the label is First Quarter, and estimated illumination is 50%. The countdown then points to the model's Full Moon boundary about 7.4 days later.
The model does not use an ephemeris, observer coordinates, moonrise, moonset, orbital perturbations, or atmospheric conditions. Treat the displayed phase time, illumination, and age as general estimates. Use an astronomical almanac for observation planning that needs verified event times.
Sound and Final beeps work only while Live is on and the page can run audio. Browser audio permission, background throttling, a closed tab, and device sleep can prevent or delay them. The page cannot wake a sleeping device.
Sources: U.S. Naval Observatory moon phase data.
Inspect a selected lunar-cycle estimate
Live uses the current device date and time. Manual mode accepts a date, hour, and minute. Set to noon provides a stable midday lookup, while Now returns to the current instant. The display estimates phase name, lunar age, illumination, and time to the next major phase.
Changing the hour on one date moves the position within the same modeled synodic cycle. Sound applies to the countdown boundary only. The result is an approximation and is not an observational ephemeris.