Moon Phases — January 2025
January 2025 contains 31 days of lunar cycle motion. The full moon falls on January 12, 2025, lighting up the night sky with roughly 98% of the lunar surface illuminated from our vantage point on Earth. Below you can explore every day of the month, see the exact phase on your birthday, a planned event, or any historical date, and scroll through neighbouring months.
Moon Phases — January 2025
Understanding the January 2025 lunar cycle
A complete lunar cycle — from one new moon to the next — takes about 29.53 days. Because our calendar month is either one day longer or one to two days shorter than that, the same phases fall on slightly different dates each month, and some months contain a phase twice while others skip it entirely. The calendar above shows the actual illumination fraction for each day, so you can see the cycle progress visually rather than relying on approximate phase labels.
Phase names mark four key moments in the cycle. “New moon” is when the Moon sits between Earth and the Sun and the near side is dark. “First quarter” falls about seven days later, when half the visible disk is lit and the Moon rises around midday. “Full moon” is another seven days on, when the Moon is opposite the Sun and fully illuminated from our perspective. “Last quarter” closes the cycle with the other half of the disk lit, rising around midnight and setting around noon.
How these phases are computed
Each day's phase is calculated from the angular separation between the Sun and the Moon as seen from the centre of the Earth at 12:00 UTC on that date. The underlying model accounts for the Moon's elliptical orbit, orbital inclination, and periodic perturbations from the Sun — the same ephemeris calculations used by amateur astronomy apps. Because the answer depends on universal time rather than your local time, a phase that ticks over at 23:30 UTC will appear on one date in western time zones and the next day in eastern ones.
The illumination percentage shown in the widget is the fraction of the Moon's near-side disk that is lit by sunlight. A full moon reads close to 100%; a new moon reads close to 0%. Phase names are assigned in bands around the four cardinal points, so a day labelled “waxing gibbous” may have illumination anywhere from about 56% to 94%. If you are photographing or observing the Moon, the live widget is the definitive source for the exact percentage and phase name on any date you choose.