The sky on Thursday, May 13, 2027
| Sun in | Taurus |
|---|---|
| Moon in | Leo |
| Moon phase | First Quarter |
| Illumination | 53% |
| Ingresses | Moon enters Virgo |
| Mercury retrograde | No |
The Moon is in Leo, near its first quarter, climbing toward full.
How long is the Moon's month?
The Moon has two different months: about twenty seven and a third days to go round the zodiac, and about twenty nine and a half days to get back to the same phase.
The shorter one is the sidereal month, the time it takes the Moon to return to the same position against the stars. The longer one is the synodic month, and it is longer because the Sun has moved on in the meantime, so the Moon has to travel a little further to line up with it again.
Phases come from the synodic month. That is the new moon to new moon cycle, and the reason phase and sign are two separate lines on a daily page: the Moon can be in Scorpio at almost any phase, depending on where the Sun is.
It also explains why calendar months and moon months never quite agree, and why a lunar year runs about eleven days short of a solar one.