Why is it that a whole one year is divided into 12 months?

Question

Can you please give me an specific explanation on how come that a whole one year is divided into 12 months

Answer 1

It appears there is more than one explanation but all are in the same general explanation

Explanatory Supplement to the Astronomical Almanac,
P. Kenneth Seidelmann
University Science Books, Sausalito, CA 94965.
http://astro.nmsu.edu/~lhuber/leaphist.html

Roman calendar
http://www.britannica.com/eb/article-9044121/Julian-calendar
also called Old Style Calendar, dating system established by Julius Caesar as a reform of the Roman republican calendar (q.v.). Caesar, advised by the Alexandrian astronomer Sosigenes, made the new calendar solar, not lunar, and he took the length of the solar year as 365 1/4 days. The year was divided into 12 months, all of which had either 30 or 31 days except February, which contained 28 days in common (365-day) years and 29 in every…
Egyptian Calendar
http://en.wikipedia.org/wiki/Egyptian_calendar
http://www.infoplease.com/ipa/A0002076.html

The ancient civil Egyptian calendar had a year that was 365 days long and was divided into 12 months of 30 days each, plus 5 extra days (epagomenes) at the end of the year. The months were divided into 3 "weeks" of ten days each. Because the ancient Egyptian year was almost a quarter of a day shorter than the solar year and stellar events "wandered" through the calendar, it is referred to as Annus Vagus or "Wandering Year".
The Chinese Calendar
The Chinese lunar year is divided into 12 months of 29 or 30 days. The calendar is adjusted to the length of the solar year by the addition of extra months at regular intervals. The years are arranged in major cycles of 60 years. Each successive year is named after one of 12 animals.
The Sumerians were probably the first to develop a calendar…
http://www.britannica.com/eb/article-9049352/lunar-calendar

any dating system based on a year consisting of synodic months—i.e., complete cycles of phases of the Moon. In every solar year (or year of the seasons), there are about 12.37 synodic months. Therefore, if a lunar-year calendar is to be kept in step with the seasonal year, a periodic intercalation (addition) of days is necessary.
Jewish calendar
http://www.myjewishlearning.com/holidays/About_Jewish_Holidays/PrimerAboutJewishYear.htm?OVRAW=who%20named%20the%20months%20of%20the%20year&OVKEY=month%20of%20the%20year&OVMTC=advanced&OVADID=1537329522&OVKWID=12847848022
The Jewish calendar stands in a creative tension between the solar and lunar years. Approximately four weeks make a lunar month. However, a lunar year of twelve months would be too short to coordinate with the solar cycle of the seasons. Therefore, seven times in every nineteen-year cycle, an entire leap month is added to the Jewish year in order to coordinate the Jewish lunar calendar with the solar year.

Bonus answers and Trivia
http://www.fi.edu/time/Journey/OnceUponATime/monthsquiz2.htm
A History of the Months and the
Meanings of their Names
http://www.crowl.org/Lawrence/time/months.html

Answer 2

In the reign of Gaius Julius Caesar the Romans were fed up with their old lunar calendar, in which the cycles of the moon decided the month and day.

Because of the inherent inaccuracies with the seasons of the earth in time with a lunar calendar, farming needed a consistent and reproducible calendar system that better enabled the planning of crop sowing.

GJC decided to consult the premier astronomical expert of the time in the development of a new calendar system:
Sosigenes of Alexandria

Sosiegenes developed for the Roman empire a reliable calendar of 365 days with a leap year every four years.

The names of the months carried over form the old roman calendar. The month July was named for GJC as a tribute to him. August was named for his adopted successor, Augustus Caesar (Imperator Caesar Divi Filius Augustus).

Pope Gregory had the calendar reformed in the 1500's since it had deviated 10 whole days since the creation of the Julian calendar in 46 BC. This Gregorian calendar, is the one most people refer to today.

Answer 3

I really don't know but if it could me 24 wow more paydays