How long is month's?

Answer 1

30 days in September, April, June and November - all the rest have 31, except for February, which has 28 (except in a Leap Year, when it has 29).

Months are linked to the Moon, but there are different ways of measuring a month.

The sidereal month is defined as the Moon's orbital period in a non-rotating frame of reference which is about 27 days, 7 hours, 43 minutes, 11.6 seconds.

A synodic month is the most familiar lunar cycle, defined as the time interval between two consecutive occurrences of a particular phase such as new moon or full moon. It is about 29 days, 12 hours, 44 minutes, 2.8 seconds.

The tropical month is the average time for the Moon to pass twice through the same equinox point of the sky. It is 27.32158 days, very slightly shorter than the sidereal month (27.32166) days, because of precession of the equinoxes. Unlike the sidereal month, it can be measured precisely.

An anomalistic month is the average time the Moon takes to go from perigee to perigee - the point in the Moon's orbit when it is closest to Earth. An anomalistic month is about 27.55455 days on average.

The draconic month or nodal month is the period in which the Moon returns to the same node of its orbit; the nodes are the two points where the Moon's orbit crosses the plane of the Earth's orbit. Its duration is about 27.21222 days on average.

Answer 2

2 3/4 years