Why do some months have 31 days, others 30 and then Feb. with 28/29?

Question

Is there any way all the months can be divided into equal numbered days?

Hey all, this question was posed to you by my 14 year old daughter, so, please, no need for sarcasm.
If you want to be sarcastic, answer my stupid questions in polls and surveys! LOL

Answer 1

No, there's no way that "all the months can be divided into equal numbered days." But this is still a VERY INTERESTING QUESTION that takes us into both astronomy and history.

The length of the year (the so-called "tropical year," which is what our calendar is ultimately tied to) is NOT the often quoted 365 1/4 days or even the other commonly seen 365.24 days. With long-determined data, it's about 365.24219 days.

This clearly presents difficulties with dividing it equally by ANY whole number of months!

The early Romans had "adjustable months" in which they inserted "extra days" fom time to time, to keep their calendar in time with what they saw that the Sun appeared to be doing. This could be very awkward for planning ahead when it was suddenly announced, "There'll be an extra day this month, guys!"

Eventually Julius Caesar decided to formalise something like the present system. Since 365.25 days (only an approximation to the year, but then believed to be accurate) divided by 12 is 30.4375 days, he decided that a largely alternating series of 30 and 31 days made the most sense. Why he chose the particular pattern with 7 months of 31 days and 4 months with 30 days is, frankly, unclear to me. That pattern adds up to 337 days, leaving February to take up the slack of 28.25 days. It could do that by having a length of 28 days for three years, then 29 days every fourth year. So that's how the "usual rule" of a leap year when the year is divisible by 4 (like 2004, 2008, ...) came into being. This system was named afterJulius Caesar, being called the Julian calendar.

Later on, it was realised that the dates were still slipping somewhat with respect to the seasons, and that further adjustments were needed. Pope Gregory consulted the world's then leading astronomers and other advisers, and introduced the Gregorian calendar. In this system, a century year is NOT called a leap year UNLESS it is itself divisible by 400. So 1800, 1900 were NOT leap years, but 2000 WAS a leap year.

Omitting EVERY century would make the average length of the year 365.24 days, while adding back in century years divisible by 400 would make the average length of the year over a 400 year time 365.2425 days. As you can see, every one of these "fine-tunings" of the calendar tweaks the average length of the year closer to what we have found is its long-term average. (It DOES vary slightly further down in less significant decimal figures.)

The Gregorian system was introduced at different times in different countries, while some places STILL continue with the Julian calendar to this day. That's one reason why Christmas is celebrated at a different time in Russia, for example, than in the West. (I believe that the 1917 "October revolution" actually happened in our November!)

The adjustment needed on switching from the Julian to the Gregorian calendar naturally grows with time. It was first a week or so. When the change was made in England in the 1750's, it was 11 days. Those 11 days just disappeared from the calendar, and RIOTS occurred because less well educated people thought that 11 days had been stolen from their lives! "Give us back our eleven days!" were the ringing cries of protest in ugly marches. By now, the necessary adjustment has reached 14 days or so, I believe.

Timekeeping is is a really fascinating subject. The present Gregorian calendar will keep the calendar in step with the seasons (ignoring the dire effects on the latter themselves due to global warming) for something like 3,300 years.

Live long and prosper.

P.S. to the questioner's parent : It's true that there are smart alecks who treat questions and questioners with disrespect. I too find them annoying, but do my best to ignore them --- although I confess that even my own guard will slip on occasion, when questioners themselves will choose as "Best Answer" something that is simply WRONG or manifestly absurd, or when a majority of voters elect to applaud a clearly smart aleck answer. You and your daughter may wish to know that her question has received a thoughtful and respectful reply from a senior professional astrophysicist.

Answer 2

The earth goes a complete orbit around the sun for 365 day and 6 hours (that is why we have one extra day on Feb every four year 6 hour x 4 = 24 hours = one day)

The month can not divided into equal numbered days because at a certain time in year the earth moves north pole (or south pole) close the the sun the warm it up. We choose that point of time as the point of the month. We can not make month even because it will change Winter/Summer/Spring/Fall every year.

Hope it helps.

Answer 3

Yes and no.

Think about it... there are 365 days in a year. If you factor that out, you get the prime numbers 73 and 5. So you could have 5 73-day months or 73 5-day months. Neither seems to work out too well.

Of course, you could also do what the Romans used to do - have months of a certain length and just add adjustment periods to re-align the calendar.

If we wanted to keep all the religious people happy, we'd still need seven-day weeks. So let's arbitrarily make every month exactly four weeks (28 days) long. If we have thirteen of these months, that gives us 364 days, so every year we'd have to have a 'leap day', and every four we'd need two (the typical leap year day).

If we make the annual leap day an international party day, I think people would go for it. I humbly suggest we call it 'Doctor Why Day'. If you like, we can name the extra month after you. ( :

See you at the party!

Answer 4

I think that it is because in ancient Greece all the months were named after someone or something important . Then later one they added some month because they need more time or something so they added months.So to keep there an amount of 365 days i think that they made the ones they thought were important long and the not so important one shorter like Feb. And about the leap year i have no clue where that can from.

Answer 5

This is all to do with Roman Emporers. If notice the months with names similar to the Roman Emporers have 31 days - July=Julius Casear, August = Augustus. January is named after the god Janus (who is the God of gates - hence it being the first month of the year - the gateway between the old year and the forthvcoming one). As these emporers were consided incredbily important it was deemed that 'their' months needed to be made more important and therefore longer.

All months originally had 30 days, but 3 were taken off February to accomadate for the extra days needed for January, August and July.

Answer 6

Are you that poor your going to argue symantics of a day difference? This is why people hate Americans. The days in a month change based on the month if you want your landlord to charge you daily take your annual rent say $800/mo x 12 months = 9600 / 365 = $26.31/day Tell Him you will pay him daily per month and since he probably wont care since its the same amount in the end you can somehow feel now life is fair again.

Answer 7

I think the system is pretty good the way it is. You know people have been working on it since the dawn of humanity and this is the best we have come up with - what is your suggestion?

Remember, it must take in to account that it's not possible to divide up the months equally so that every month has the same number of days if the time of each day is 24 hours long!

Answer 8

Actually its because the year has 365 days. When Feb has 29 days, then the year has 366 days because each year adds 1/4 of a day! so every 4 years there is an extra day in Feb to even out the days!
i have no idea who the hell came up with it!

Answer 9

There are approximately 365.25 days in a year.

365.25/12 is not an even number, so there has to be some inconsistencies... each month would need 30.4375 days... so some get 30, some 31.

February is an oddball month. See the link for some interesting facts! :)

Answer 10

No, because 12 does not go into 365 1/4 evenly.
There are 365 1/4 days in a year