why do certain months have 30 days and others 31?
926140
http://en.wikipedia.org/wiki/Gregorian_calendar
763017
February used to have 29 days and 30 - in leap years - before Augustus Caesar's ego messed it up.\n\nThe Roman year began in March and February was the 12th month. After June came Quintus (the 5th month) of 31 days and Sextus (the 6th month) of 30 days. Followed by September (the 7th month), Julius Caesar decided to name Quintus after himself and we now know of it as July. \n\nThen when Augustus Caesar became Emperor he decided he would change the name of Sextus and name it after himself. As that would mean his month has one day less than July and imply he was a lesser emperor than Julius Caesar had been, he decreed that August should have 31 days not 30 and he therefore lopped a day off February,\n\nSo your proposal merely seeks to restore us to the calendar as it was prior to Augustus Caesar's interference,\n\nThe Babylonians with their sexagesimal (base-60) counting system which gave the world 360 degrees in a circle, also had 360 days in a year and 12 months of 30 days, Unlike the French solution, they added their extra days in the form of a 13th month, once every 6 years.\n\nThe French Republican calendar was a thorough overhaul of the system, introduced in the context of the world's first metric system, and involved not only 12 30-day months but 3 10-day weeks in a month, 10 hours in a day. 100 minutes in an hour and 100 seconds in a  minute. The months had new names, the year began in the autumn and Year 1 was the date of the Declaration of the French Republic\n\nClocks were built to tell the time by these rules but they did not catch on. Napoleon officially abandoned the calendar on 1st January 1806, after little more than 12 years of use. It briefly resurfaced and re-emerged again at the time of the Paris Commune in 1871, but it has not exactly attracted swarms of advocates before or since.\n\nMy conclusion is that people are set in their ways, see no great pressing need for change and that as there is no exact, mathematically neat solution to the fact that a year is not an exact number of days (nor is a lunar month either) whatever system we use will be a bit inelegant, and acknowledging that, most people would say "let's stick with what we have got. It's easier. Then we don't have to learn anything new."\n\nInertia, apathy and habit will all argue against change, I fear! However logical the change may be.
990038
In Ohio it is 30 days
461101
all month has 28 days in a year
860193
About 8 in the whole month
99578
The length of the months is an arbitrary invention of humans.  Look at the names - SEPTember, OCTober, NOVember, DECember = 7th, 8th, 9th and 10th month?  Augustus Caesar took a day from FEB to add to AUG when he named AUG after himself.
573796
In the Egyptian calendar, every day was a holy day of some significance. There were 12 months with 30 days each, and 5 days which were set outside of the year when the Gods were born. The most significant thing about the Egyptian calendar was that it did not allow for a leap year, and was in effect for thousands of years, so over time, the months shifted in relation to the year, and seasonal celebrations lost their original meanings while being carried on religiously.
908181
Yes, 31/30 is an improper fraction which can be changed to 1 and 1/30. You then add 1 1/30 to 56 for a total of 57 and 1/30. :)
35451
Originally, the Roman calendar had 12 months of 29 or 30 days, beginning in March, with an extra (intercalary) month thrown in every other year to get things back in sync with the seasons. \n\nUnfortunately this led to abuses, as officials added or dropped intercalary months to extend their time in office or to hasten elections. \n\nSo in about 45 BC, Julius Caesar, who by now had made himself dictator of Rome, established a 365-day calendar with leap years. For reasons unknown to me but which seemed good to him at the time, he decided that instead of having five months with 31 days and seven with thirty, he would only allow February to have 30 days in a leap year. He incidentally renamed the fifth month, Quintilis, after himself (Julius, or July). \n\nJulius' adopted son and heir, Octavian, gained control of the state a few years after Julius' assassination in 44 BC. Octavian ruled so well that the Senate granted him the name of Augustus, and after his death he was formally deified by the Senate. As part of this, the month Sextilis following July was named August, just as Augustus had followed Julius as leader of the State. But since the month now named after the God Augustus had only 30 days, another day was taken from poor February and given to August.
84324
A widely believed--but possibly erroneous--story has it that February is so short because the Romans borrowed a day from it to add to August. August was originally a 30-day month called Sextilis, but it was renamed to honor the emperor Augustus Caesar, just as July had earlier been renamed to honor Julius Caesar. Naturally, it wouldn't do to have Gus's month be shorter than Julius's, hence the switch.\n\nBut some historians say this is bunk. They say February has always had 28 days, going back to the 8th century BC, when a Roman king by the name of Numa Pompilius established the basic Roman calendar. Before Numa was on the job the calendar covered only ten months, March through December. December, as you may know, roughly translates from Latin as "tenth." July was originally called Quintilis, "fifth," Sextilis was sixth, September was seventh, and so on.\n\nTo meticulous persons such as ourselves, Randy, having the calendar run out in December and not pick up again until March probably seems like a pretty casual approach to timekeeping. However, we must realize that 3,000 years ago, not a helluva lot happened between December and March. The Romans at the time were an agricultural people, and the main purpose of the calendar was to govern the cycle of planting and harvesting.\n\nNuma, however, was a real go-getter-type guy, and when he got to be in charge of things, he decided it was going to look pretty stupid if the Romans gave the world a calendar that somehow overlooked one-sixth of the year. So he decided that a year would have 355 days--still a bit off the mark, admittedly, but definitely a step in the right direction. Three hundred fifty five days was the approximate length of 12 lunar cycles, with lots of leap days thrown in to keep the calendar lined up with the seasons. Numa also added two new months, January and February, to the end of the year. Since the Romans thought even numbers were unlucky, he made seven of the months 29 days long, and four months 31 days long.\n\nBut Numa needed one short, even-numbered month to make the number of days work out to 355. February got elected. It was the last month of the year (January didn't become the first month until centuries later), it was in the middle of winter, and presumably, if there had to be an unlucky month, better to make it a short one.\n\nMany years later, Julius Caesar reorganized the calendar yet again, giving it 365 days. Some say he made February 29 days long, 30 in leap year, and that Augustus Caesar later pilfered a day; others say Julius just kept it at 28. None of this changes the underlying truth: February is so short mainly because it was the month nobody liked much--a judgment with which I heartily concur. Frankly, if the Romans had cut it down to 15 minutes, it wouldn't have bothered me a bit.
615992
for the duration of the month of may
143192
Here's one way... there may be others....\n\nMake column A the "input" column (where you type in the # of days).  Make column B, C, and D "output" columns which displays the # of years, months, and days respectively.  Input the following formulas:\n\nCell B2:  =TRUNC(A2/365)\nCell C2:  =TRUNC((A2-(B2*365))/30)\nCell D2:  =MOD((A2-(B2*365)),30)\n\nHope this is what you are looking for...
366634
It gives us our months of the year
558487
It's not always exactly every 30 days.  It could be 33 or 35, especially at first.  Don't worry unless you think you're pregnant.  Talk to your mom about it or sister or older friend.
623290
It is because you are trying to make a round peg fit into a square hole.\n\n7 x 4 = 28 x 13 lunar months = 364 days, \nbut there are 365 days in a regular year. \nThen in order to fit into the Earth's rotation around the Sun every 4th year we have to add an extra day.\nPlus occasionally we have Leap seconds too.\nConfused?
1176246
29 - 30 - 31 depends from the month!
839464
About 30 days with average activity.