Lunar Phases

What it's for

Find out what the Moon is doing on any date: its phase, how much of its face is lit, how many days old it is, and when the next new moon and full moon come. A table lists every new, first quarter, full and last quarter moon in a month you choose.

For example, when you are planning a night of stargazing or photography around a full moon, or checking the phase on a date in a photograph.

How to use it

Pick a Date and time (it starts at the current time; Now sets it again) and the phase appears with its age and the next new and full moons in your own time zone. Pick a Month to list for the main phases in it, shown in your time and in UTC. Months are split at UTC midnight, so a phase near the start or end of a month in your zone can appear in the next or the previous month’s list.

The times come from Jean Meeus’s method for the Moon’s phases (Astronomical Algorithms, chapter 49). Nothing is sent anywhere.

Example

Set Month to list to 2024-01. The table shows the last quarter on 4 January at 03:30 UTC, the new moon on 11 January at 11:57, the first quarter on 18 January at 03:52 and the full moon on 25 January at 17:53. With the date and time set to 25 January 2024 at 17:54 UTC, the phase is Full Moon, 100% lit.

Good to know

Times are the Moon’s phases to within a few minutes (the tests check them against published times within ten minutes) for dates from 1800 to 2150; the further from today, the less reliable the clock correction (ΔT) is. The share of the face lit and the age are worked out from the main phase times, so they are close but not exact, and the lit share can differ by a percent or two. Moonrise and moonset aren’t included: they depend on where you are. The picture is a small drawing, and in the southern hemisphere the Moon looks turned the other way up.