Moon phase calendar

The phases of the Moon

The Moon has no light of its own. The Sun always lights half of it, and as the Moon circles Earth, we see more or less of that lit half. At the New Moon, the lit half faces away from us, so we can't see it. Then the Moon waxes, growing to the First Quarter, when half the disk is lit, and on to the Full Moon, when the whole disk is lit. After that it wanes, shrinking back through the Last Quarter to the next New Moon. The whole cycle takes about 29 and a half days. Between those points, a crescent Moon is less than half lit and a gibbous Moon is more than half lit.

In astrology, the cycle has two halves. The waxing half, from New Moon to Full Moon, is traditionally a time to start things and build on them. The waning half, from Full Moon back to New Moon, is a time to finish and let go. It's tradition, not a rule.

How the phases are calculated

We find each New Moon, First Quarter, Full Moon, and Last Quarter to the minute from the positions of the Sun and the Moon. Everything is worked out for the place you've chosen, in its local time. If you haven't chosen one, it's worked out for Greenwich, in Greenwich Mean Time (GMT). Each day on the calendar shows the Moon as it is at noon there and the sign it's in at that hour.