Instead of this business of the months having 30, 31, or 28 days, or even 29 days, why aren’t there just 13 months that all have 28 days? 365/13=28.0769 Wouldn’t it have just been easier to asign the days each a few more minutes or seconds than to have months of varying days and leap year too?
Actually, Scott Flansburg (the “Human Calculator”) has done exactly that: designed a calendar of 13 months of 4 weeks each of 7 days each (364 days) with each year beginning on Day Zero (which is the 365th and has no month or weekday name) and a Leap Day every four years (which also falls between months–don’t remember which ones–and also has no weekday name). Each Month starts at the beginning of the week and ends at the end of the week. In addition, every date (such as the 17th) falls on the same weekday every month every year. Pretty cool, really. He’s trying to get it adopted worldwide, but probably won’t. People are too traditionalist. You can find out about it (and buy one, if you wish) at http://www.simpleage.com
As to why are there not 13 equal months I am sure it has something to do with the history of our calander but I am not knowledgeable on that subject.
As to assigning days a few more minutes or seconds you can’t do that. In our time keeping system there are two defined units, the day and the year. One day is the time it takes for the earth to rotate once about it’s axis so we can’t just add time on to the day.
Do you really think that our calling 24 hours a day isn’t an aproximation? How likely is it that the earth’s rotation is exactly 24 hours, and not something like 23 hours, 59 minutes and 38 seconds? Or 24 hours, 2 minutes and 13 seconds? I don’t think that the addition of a few seconds or a couple of minutes would make it any less inaccurate than it already is.
Perhaps the moon revolves around the earth only (approximately) 12 times in one year. A more detailed history of the calender is linked here: http://es.rice.edu/ES/humsoc/Galileo/Things/gregorian_calendar.html
If I got it right, the calender evolved from a (possibly apocryphal) 10 month calender.
I don’t think our calling 24 hours a day is an aproximation. I think that one day is devided up into 24 equal periods that we call an hour. A day is a defined period of time. It is how long it takes for a planet to rotate about it’s axis once. If we want to change our methods of recording time that is not a problem but you can not change how long a day is or how long a year is because they are defined by astronomical events.
Our definition of a day is based on the time it takes for the sun to move from a position directly over the meridian, around the earth to end up in that position again. However, the rotation of the earth on its axis takes slightly less time than this, because as the earth moves around the sun it causes the sun to rise later each rotation.
One of these days is called a “sidereal” day, and the other is called a “solar” day. I forget which is which :o.
Uhh…OK
This doesn’t really effect my main point which is that a day is a defined period of time while hours, minutes etc. are derived periods of time. ie you can’t define them with out reference to another measurment of time. Yes?
No, it doesn’t. I just wanted to throw that in there.
Well, I always was taught that a day was 23 hours 56 minutes and that 24 hours was an approximation (one reason why the metric system only uses seconds as a measure of time, and defines a second as a fraction of a year).
As for the twelve months, there are a lot of reasons why that’s more convenient – easier to divide the year, avoiding the superstition about the number 13. There are moon generally 12 full moons (or new moons) a year, so that was used as the basis for a month.
Scott Flansburg is hardly the first person to propose a 13-month calendar, and he’s probably not going to be the last. But calendar reform is a matter of great apathy and the last attempt – French revolutionary calendar – was quickly abandoned.
Triskadekaphobia is indeed the leading reason why we don’t have a 13-month calendar year, even though there are 13 lunar cycles per year.
The 23:56 day is actually the lenght of time it takes the Earth to rotate 360[sup]o[/sup], known as a sideral day. The solar day is the time from noon one day to noon the next, which is indeed 24 hours long, give or take a fractional second due to rotational eccentricities.
Chuck, you’re thinking of the difference between the sidereal and the solar day. You’ll notice if you multiply it out that the 4 minutes we lose each day adds up to about 14400 minutes = 24 hours = one day over the course of the year … this is the difference between the actual rotation speed of the Earth and the rotation speed relative to the sun as the Earth revolves around it. If we used the actual sidereal day (based on the Earth’s rotation relative to the ‘fixed stars’) as our day, then sunrise would rotate through the day as the year went by-if we started the calendar year in sync, then around June we’d have sunrise about 6 PM and sunset around 6 AM. This would, in layman’s terms, suck. 
The 24 hours we use are almost exactly one solar day, except that the rotation speed of the Earth is slowly decreasing-that’s why we get those ‘leap seconds’ that you hear about once in a while.