Lunar Month

Introduction

From the study of the moon’s constantly repeating cycles we have the lunar calendar which comprises of 12 more or less equal time periods, called months.

Month

The word month itself has its roots in the word Moon, rightly so as a month is the time taken for the Moon to complete one cycle that is from new Moon to new Moon again.

New Moon

Please note ‘new Moon’ is the phase of the Moon where no Moon can be seen in the night sky, this is because the Moon is right in between the Earth and the Sun. Light from the Sun hits the side of the moon closest to it and illuminates it but the side of the Moon facing the Earth remains unlit by the sun and consequently the Moon appears fully dark to us.

Lunation and its Duration

Lunation is another word for a month as defined in the section above. A lunation on average takes 29.53 days.

Why 12 Months in a Year?

A solar year is defined as the time taken for the earth to orbit the sun. This has been measured to take 365 days.

So the answer to the question “Why are there twelve months in a year?” can be answered by saying that the year calendar that we currently use here in the West is half solar and half lunar. Its overall governing parameter is the solar year, that is one year has 365 days in it, and to divide the year into months, 12 whole lunar months fit into the a solar year.

The calculations below show how the number 12 is derived and the reason why some months have more days than others.

If we were to multiply 12 by the average lunation period or lunar month time which is 29.53 days we end up with 354 days. Meaning 11 days are unaccounted for.

So to make up these missing 11 days some months get more than 29.53 days such as there being 31 days in January and March and 30 days in April etc. etc.

End.