Moon Phases This Month, and the Next Year

Below is every new moon, first quarter, full moon and last quarter for the next fourteen months, computed from orbital elements rather than copied from anywhere, and accurate to within about two minutes of the times published by the US Naval Observatory. Times appear in your own time zone if your browser reports one, and in UTC otherwise, which matters more than it sounds: a full moon at 23:40 in London is the following day in Berlin, so any calendar that prints a bare date is wrong for roughly half the planet.

How to read this, and how not to

A lunar month runs about 29.53 days and the four quarters divide it evenly, so the pattern repeats but never lands on the same dates twice. That is the whole reason a fixed calendar cannot hold it and a table like this has to be computed.

What this table is not is a forecast for your body. There is no reliable evidence that the phase of the moon determines when your period arrives, and the research is more contested and more interesting than either the believers or the debunkers usually admit, which is worth reading properly before you draw conclusions from any alignment you spot here. If your period happens to land on a full moon this month, the honest reading is that it landed on one of eight roughly equal possibilities.

The useful thing you can do with an almanac is the same thing you can do with any calendar, which is notice. If you keep a record of when your period starts, you can lay it against these dates after a few months and see for yourself whether anything holds. Most women find nothing, and that is a real answer rather than a failed one. Some find their cycle drifting steadily against the lunar month, which is exactly what two similar but unequal rhythms do to each other.

Where these numbers come from

The phase times are calculated from the standard periodic terms for the Moon's orbit, the same method almanacs have used for decades, which accounts for the fact that the Moon's orbit is elliptical and pulled around by the Sun. A simpler average of 29.53 days is easy to write and drifts by up to twenty hours, which puts it on the wrong calendar day about a third of the time. That is the difference between a table you can rely on and one that is quietly wrong twice a season.

Every value here was checked against the US Naval Observatory's published phase times before this page shipped, not against our own arithmetic. If you find one that disagrees with your national observatory by more than a couple of minutes, that is a bug and we would like to know.

This article is for educational purposes and is not medical advice. Nothing on this page describes a proven biological effect of the moon on menstruation. If your periods are irregular, unusually heavy, lasting more than seven days, or accompanied by bleeding between periods, please see a doctor. Any bleeding after a full year without a period should be checked promptly.