The eight moon phases explained
Four principal phases are exact instants; the four in between are the days that connect them. A moon phase is the shape of the sunlit part of the Moon as seen from Earth. It changes as the Moon orbits the Earth every 29.53 days: from new moon, when the lit side faces away, through first quarter and full moon to last quarter and back. The phase times on this page are computed with the algorithms of Jean Meeus and agree with almanacs to the minute.
- A lunar month, from one new moon to the next, lasts 29.53 days on average.
- Moon phases are the same everywhere on Earth at the same instant; only the local time and the tilt of the crescent differ.
- Today: waning gibbous, 99%.
Moon between Earth and Sun; not visible.
A thin sliver grows on the right after sunset.
Half lit; highest at sunset.
More than half lit and still growing.
Fully lit; rises at sunset, sets at sunrise.
More than half lit and shrinking; rises late in the evening.
Half lit; highest at sunrise.
A thin sliver before dawn.
Questions people ask
What phase is the moon in today?
The phase and illumination for today are in the first line of this page; they are calculated for the current time in the Europe/Vilnius zone.
When is the next full moon?
The next phases strip shows the date and time of the next full moon, and the table below lists every full moon of the year.
What is a moon day?
A moon day counts the days since the last new moon: the first moon day starts at the new moon, the fifteenth around the full moon. The count on this page is the whole number of days since the last new moon plus one.
Is the moon waxing or waning?
Waxing means the lit part is growing (from new moon to full moon); waning means it is shrinking (from full moon to new moon). In the northern hemisphere a waxing moon is lit on the right.
Why does the full moon time differ between sources?
The instant of full moon is the same everywhere; sources differ only in the time zone they print. This page shows UTC in the tables and local time in the strip.
Does the full moon affect sleep?
Several studies found that people fall asleep later and sleep less in the days around the full moon; others found no effect. Where it appears, the difference is small.
How are the phase times calculated?
With the algorithms published by Jean Meeus in Astronomical Algorithms (1998), including the periodic terms, which give the phase instants to about one minute.
- Jean Meeus, Astronomical Algorithms, 2nd ed., Willmann-Bell, 1998, chapters 48 and 49.
- NASA Eclipse Web Site (eclipse dates and visibility).
Numbers update through the day from public sources. The text for each day is written from that day’s data and checked by the editor. Every past day keeps its own page in the archive.