why is a month 30 & 31 days long?

Question

has anyone ever think why the days of the months are 30 & 31 except February when the days between new moons are 28.Isn't a month suppose to be as long as a new moon phase as the hrs of a day is the rotation of the earth and the length of the year is the earth's revolution around the sun.

Answer 1

It takes the Moon 28 or 29 days to orbit the earth but most months are 30 or 31 days long.

This has resulted from a compromise. Initially, months were mostly 29 days long and the average length of a month was 29.5 days which is the time taken by the Moon to orbit the Earth. However, this resulted in a year of only 354 days while the orbital period of the Earth is 365.2422 days. As a result, the calender became out of sync with seasons which was bad. This was initially corrected in an arbitrary way by adding a 13th month, but soon the calender was thrown into severe confusion.

In 46 B.C., Julius Caesar reformed the calender by ordering the year to be 365 days in length and to contain 12 months. This forced some days to be added to some of the months to bring the total from 354 up to 365 days. To account for the extra 0.2422 days, every fourth year was made a leap year. This made the average length of a year to be 365.25 days.

However, the Julian year still differs from the true year and by 1582, the error had accumulated to 10 days. So, 10 days were dropped from the year 1582 so that October 4, 1582 was followed by October 15, 1582. In addition, a modification was made that century years that were not divisible by 400 would not be considered as leap years. For example, 2000 would be a leap year while 2100 would not. This made the year sufficiently close to the actual year and this calender is called the Gregorian calender.

As the year is now set up to follow the seasons accurately, it no longer follows the phases of the Moon.

Answer 2

Because 365 divided by 12 is 30.4. So we have to switch between 30 and 31. February is extra short because of a couple of Roman Emperors, Julius and Augustus, who thought "their" months should have 31 days.

The orbit of the Moon has nothing to do with the orbit of the Earth around the Sun. So moon cycles and annual cycles do not line up. There are 12.38 lunar months in a solar year. If we used the moon exclusively for our calendar-keeping, our months would be 29 and 30 days, but our year would be 11 days short. (In fact, the Islamic calendar does just that, drifts backwards 11 days every Gregorian year.) Luni-solar calendars, such as those used in Asia and by Jews, use a 19-year cycle, which inserts extra lunar months in certain years to keep everything synchronized, eventually. We in Euro-America have given up on the Moon and stretched our months to accommodate the Sun exclusively.

Answer 3

Originally, months were exactly from a Moon phase back to the same Moon phase. The word "month" is from the same root as the word "moon".

In fact, many calendars still work that way: Chinese calendar goes from New Moon to New Moon (Chinese New Years is the second New Moon after the winter solstice).

Muslim calendar is purely lunar (12 lunar months = 354.37) that is why their dates drift "forward" by about 11 days for every Gregorian year. Jewish calendar follows a 19 year cycle of 12 and 13 lunar months, to keep it (over long periods) in synch with with Solar calendar.

We inherited our calendar from the Romans who designed it after understanding (from the Eyptians, perhaps) the importance of the return of the seasons for various reasons (agriculture, commerce, war).

However, they wanted to retain the 12 periods of the year called months. So, they took the 365.25 days of a year and divided them into 12 to get 30.4.

They decided on 6 months of 31 days, 5 of 30 days, and the last month of the year with 29 days (with an extra day -- for 30 -- once every four years).

The first month of the year was Mars, named after the god of war. The year started then because life in Rome was centred on war and the armies. Before March, the soil was too wet and boggy for armies to get anywhere. After December, if the armies were not back, they be stuck somewhere until March.

1. March (war) 31 days
2. April (to open -- as in flowers) 30 days
3. May (Maia, goddess of plants -- a.k.a. Mother Nature) 31 days
4. June (Juno -- motherhood, chilbirth) 30 days
5. July (from Julius -- Caesar; named after his death) 31 days
Hereafter, the months were simply "numbered"
sexember, september, october, november, december (literally : 6th, 7th, 8th, 9th, 10th).

After that, the period during which war could not be waged had no official month names. Religious calendars (which needed dates throughout the year) brough in Janus (a god with two faces, looking over doors and gates -- he could look both ways) and Februarius (month of fevers).

When Julius's grandson became emperor, he was vain enough to have himself proclaimed "Augustus" (the most glorius one). He wanted his own month, just like Julius. He could not displace any of the previously named ones, nor could he place himself ahead of Julius (who the Romans considered a god). Therefore, he took the following month.

Of course, he had to have 31 days as well. That changed the entire sequence. It also required the last month (February) to lose yet another day.

That structure has not changed since. The date at which we celebrate a new year has moved around: March 1, Easter, April 1, January 1.

January 1 has its turn more often than once. At one point in the Roman religious calendar, Janus gained the ability of not only looking both ways, but of being able, with his two faces, to see the past and the future: he was a natural for the passage from the old year to the new.

During their revolution, the French created a calendar with 12 months of exactly 30 days (three "weeks" called decades, of ten days each), plus 5 bonus days at the end of the year: extra vacation for everyone -- these days did not belong to any month. On leap years, a 6th bonus day was added.

In this way, whatever the year, a date would always fall on the same day of the "week". The 5th. 15th and 25th days of a month were always on the day called Quintidi (latin for 5th day).

Answer 4

February has 28 days using fact Julius Caear and Augustus Caesar had rather massive egos. Julius took away an afternoon from Feb, from 30 to 29 days. He did provide it 30 days in a bounce year. The day became transferred to his month, July. Augustus did no longer want to be overwhelmed so he took yet another day from Feb, and placed it in his month, August. I forgot who the subsequent emperor became, yet he declined having a month named after him, asking what might ensue whilst the thirteenth emperor got here alongside. And so February became stored!

Answer 5

The roman's messed about with the length of months, various emperor's added extra days to their months, July is named after Julius Caeser & August after Augustus, a lunar month is actualy 28.5 days so lunar calenders are usually based on two months equalling 59 days. 13 times 28 is 364 so a lunar calender would quite quickly get completely out of step with the seasons, who fancies taking their August holidays in mid-winter (Australians etc excepted)

Answer 6

In Ethiopia all the 12 months are 30 days long,and the 13th month 5 days long.

Answer 7

because a month is based on the orbit of the moon. and it takes that long for the moon to orbit the earth.