Talk:Julian year

Julian year v. Julian calendar

AFAIK, Julian years are used strictly by astronomers, and not by historians, and are not implied to correspond exactly with years in the Julian calendar, since they use an average value, while the calendar uses a variable value. The recently added paragraph (With historical documents...) does not seem to be appplicable to this article. The reference to Old Style v. New Style is irrelevant, since the Julian year does not always begin exactly on January 1.0, nor was it ever intended to be used with "historical documents". --Nike 21:08, 28 September 2005 (UTC)[reply]

As Churchill said of Chamberlain "He views foreign policy from the wrong end of a municipal drain" (The Chamberlain family made their political reputation in local politics in Birmingham). I think you are being myopic. A year in the Julian calendar is a "Julian year". The start and end dates of a year are relevant. Just because it has a definition used by astronomers does not mean that it can not have another definition as well. -- Philip Baird Shearer 14:45, 29 September 2005 (UTC)[reply]

You are referring to the Julian calendar year, which is quite distinct from the Julian year referred to in the article. If you wish to distinguish them, then you should create a disambiguation page. --Nike 02:16, 30 September 2005 (UTC)[reply]

"since it provides quick and simple conversion to Julian dates." Please explain how one can have a simple conversion to Julian dates if one does not take account of the start of a year? Philip Baird Shearer 07:05, 30 September 2005 (UTC)[reply]

The start of which year? The epoch for Julian year J2000.0 is January 1 2000, Gregorian, at 11:58:55.816 UTC, and converts to Julian date 2451545.0. Julian year 2001.0 converts to 2451545.0 + 365.25 = JD 2451910.25. That's December 31 2000 17:58:55.816 UTC. Now, if you want to talk about Julian calendar years, January 1 on the Julian calendar falls on January 14 on the Gregorian calendar in this century. --Nike 04:28, 1 October 2005 (UTC)[reply]

Why do you assume that all Julian years start on the 1st of January? Philip Baird Shearer 16:59, 1 October 2005 (UTC)[reply]

I do not assume that at all. Some Julian years start on December 31 Gregorian. That is because of the way that Julian years are defined. The Greogian calendar year 2000 was a leap year, which means it was 366 days long, but the Julian year was 365.25 days, so J2001.0 started before January 1, i.e. December 31. Note that we're not even talking about the Julian calendar, which is where you are getting confused. That year doesn't start until January 14 in the Gregorian calendar. And Julius Caesar, himself, set the beginning of the Julian calendar year as January 1, so this predates the term by 18 centuries. The distinction between "Old Style" and "New Style" have nothing to do with the subject of this article, which is specifically about a modern astronomical term. What you really need to distinguish is the difference between a Julian year and a Besselian year.

Let me state this as clearly as I can. This article is about the intervals defined by astronomers as being exactly 365.25 SI days, each beginning at a defined epoch. They are named such because the interval length is equal to an average year in the Julian calendar, but they have epochs close to the beginning of Gregorian calendar years. They were never intended for dating previously existing historical documents.

Julian years are not Julian calendar years, in spite of the name. Nor are "Julian dates" dates in the Julian calendar. --Nike 05:36, 2 October 2005 (UTC)[reply]

You are stating that a Julain year is not a Julian calendar year. But as I said above: I think you are being myopic... etc. If someone says the word cricket to most English men they think sport not insect. If someone says "football" to an Americans they think girdiron not soccer. An extra paragraph in this article to help people who do not have the same mind set as you does not mean that it is wrong. Philip Baird Shearer 11:12, 2 October 2005 (UTC)[reply]

The Julian day system was intended to provide astronomers... This is the Julian year article, not the Julian day article. They are two entirely different things. Also, Charles I was executed January 30, not January 29.

Regarding your last statement, in Wikipedia this is referred by the term "disambiguation". That is, these are two different things which have the same or similar name. There are set guidelines in place to deal with this, which I have already applied to this article. The statements you keep adding do not disambiguate, but further confuse the two different terms. I think that where you really want to post this is in the Julian calendar article. That is where mention of New Style v. Old Style actually makes sense. Also, read the Year article for more information about different kinds of years. --Nike 05:35, 3 October 2005 (UTC)[reply]

I have entered this page on WP:RFC as a few more editors may help to settle the issue. I have entered it under two areas as they will be looked at by different communities of editors:

The text of the entry is:

Talk:Julian year What is a "Julian year"? Is it restricted to astronomic time interval, or can it have also have a historical context as well? Two editors disagree on this and some other editorial input would help to settle the issue. 07:08, 3 October 2005 (UTC)

--Philip Baird Shearer 07:15, 3 October 2005 (UTC)[reply]

As I have said repeatedly, we are talking about two different things. A Julian year, as defined by astronomer, is very different from a Julian calendar year. Since the latter could be called by the same name (it is called "Julian calendar year" to distinguish it) this raises the issue of disambiguation. Wikipedia has a clear policy on how to handle disambiguation. You do not shoehorn two things with the same name into a single article; each gets a separate article. Since the Julian calendar already has an article, I added a disambiguation linking to that article. That is the appropriate place to discuss OS/NS. (But it should also include all the historical variations in the Julian calendar, which has been used by many countries over the past 2000 years, not just England.)

Also, you keep posting your comments in reference to Julian days, even though this is the Julian year article. --Nike 21:52, 3 October 2005 (UTC)[reply]

In the interest of resolving this dispute and disambiguation, I have renamed this article to "Julian year (astronomy)", so that there is no ambiguity. This article refers solely to the astronomical unit, not to the Julian calendar. --Nike 22:35, 3 October 2005 (UTC)[reply]

First of all, you had a typo in your rename ("astonomy"). But also, since we don't have any other "Julian year" article, disambiguation is superfluous. And in fact it's hard to imagine what you could put on such a page that isn't already found at Julian calendar. -- Curps 23:49, 3 October 2005 (UTC)[reply]

The desputed paragraph which I added and Nike keeps deleting is:

The Julian day system was intended to provide astronomers with a single system of dates that could be used when working with different calendars and to unify different historical chronologies, but with historical documents there is a complication which makes using a simple Julian year calculation inappropriate. The start of the year has varied over time and from place to place so there can be a difference under which year an event take place. For example the execution of Charles I of England is usually recorded as having taken place on January 30 1649 ("New Style" (NS)). But in contemporary documents it is recorded as having taken place on January 30 1648 because the start of the year in England at the time was March 25 ("Old Style" (OS)).

--Philip Baird Shearer 08:47, 4 October 2005 (UTC)[reply]

First of all, this paragraph is talking about "The Julian day system", which is not even the subject of this article, but has its own article. More importantly, the Julian years described by this article are not used to date historical events, such as the executions of kings. They are used for astronomy. Old Style and New Style dates have nothing to do with Julian years. I do not know what is so difficult to understand about that. Julian years do not begin on either January 1 or March 25 on the Julian calendar, but on or just before January 1 on the Gregorian calendar, 13 days before the same date on the Julian calendar. They are called Julian years because their length is based upon the average Julian calendar year, but that is their only connection. --Nike 18:43, 4 October 2005 (UTC)[reply]

I believe that in astronomy, the Julian year is primarily or exclusively used as a unit of time, that is, as a measure of duration (this is reflected by its classification under Category:Units of time. The orbital period of Pluto or Neptune might be expressed in Julian years, for instance, simply because it's inconvenient to state "59800 days". The fundamental international-system unit of time is the second, but it's convenient to define 86400 seconds as one day and 365.25 days as one Julian year, because you don't want to deal with impractically large numbers and these are units whose scale is intuitively understood, yet easily intercoverted with one another without too many messy fractions.

You would never hear astronomers say "such-and-such event occurred on February 23 in the Julian year 2005" or "on February 23 2005 in the Julian calendar". Astronomers don't use the Julian calendar at all... when they mention specific dates (the future date of an eclipse for instance), they use the Gregorian calendar like anyone else. In other words, the use of the Julian year in astronomy doesn't make references to months or names of months or days of the month or "what year it is". It's just a synonym for 365.25 days, just like a mile is a synonym for 5280 feet.

Astronomers do use Julian days, but these have nothing to do with the Julian calendar or even with the astronomical Julian year, it's just a running count of days with an arbitrarily chosen starting point in the distant past, with each day number one greater than the previous, without reference to months or years. Although sources differ, it is likely not even named after the same Julius (Caesar) as the Julian calendar. A Julian year isn't 365.25 "Julian days", it's just 365.25 days... a Julian year is a unit of time and not a running count, but a Julian day is a running count and not a unit of time.

Note that the J2000 epoch refers to an exact moment in time, it's not a timekeeping system. It's just a convenient name, reflecting the chosen sychronization with the Gregorian calendar date January 1 2000 (but they could have picked any other arbitrary point in time). This is no different than "3-1/2 inch disks" or "35 mm film"... there are no 3.6 inch disks or 37 mm film, the "35 mm" is just a name for a standard, they could have just as easily picked an alphabetical name like "Beta" or "VHS" but they were unimaginative and picked a numerical name. Likewise "J2000" is just a name, you would rarely if ever hear someone say "the present time is precisely J2005.875234" (this would have a precise meaning, but note it would be completely out of sync with the Julian calendar because J2000.0 is synchronized to the Gregorian calendar January 1 2000, and it would be out of sync with the Gregorian calendar as well after few hundred years, so it's not particularly useful for timekeeping purposes). Consider the Unix epoch of 1 January 1970, which could just as easily have been called "U1970" if someone had wished to. A numerical name for the J2000 epoch is convenient in one sense, namely because for practical reasons it is necessary to change epoch every now and then (for instance, so that star charts don't differ too much from reality due to precession), and when a new epoch is needed it will probably be named something like J2100, and this name will conveniently reflect that it will be exactly 36525 days from J2000.0 and not 100 calendar years.

On the other hand, the naming and numbering of Anno Domini years in conjunction with 12 named calendar months and days of the month according to the Julian calendar is an entirely different topic that belongs in a separate article from this one. We could disambiguate and create a Julian year (Julian calendar) or a Julian year (disambiguation) or more clearly First day of the year in various countries and historical time periods, but it seems that the information in the added paragraph is really a subtopic rather than a topic in its own right. It's information that logically should be incorporated into the Julian calendar article (and perhaps already is), and would only really need to be broken out into a separate article for reasons of length (as in the "History of X", "Geography of X", "Demographics of X" for country "X" are often broken out into separate articles, or as in Mars in fiction which is now a separate article from Mars, in each case with a link from the main article.

If you really wanted to have a thorough discussion of what was considered the first day of the year in every known historical time and place, it might be enough material to make up a separate article. Just not this one. The usual Wikipedia convention is that separate topics belong in separate articles.

-- Curps 20:58, 4 October 2005 (UTC)[reply]

We may need an article on the a year in different clandars (see the articles on Japan for an interesting problem of mapping the first day of the Gregorian calandar. It is often translated as January 1st but apparently this is not correct. But this is not the article where that belongs.

As I said above the term is not specific enough to be exclusively understood as an "astronomical Julian year". Personally I do not think that there is enough information, or that the information is diverse enough to justify two articles. However as the two of you do. Then so be it. Philip Baird Shearer 21:35, 4 October 2005 (UTC)[reply]

You may be correct that the term is not specific enough. But this is a very common problem and Wikipedia has specific methods of dealing with it. Wikipedia does not support including two different things in the same article just because they have the same name. There are already two articles, Julian year and Julian calendar. A disambiguation notice has been placed in the former that links to the latter. As Curp said, there is no need for an article about the other type of Julian year, since it is already covered by Julian calendar. There is also an existing article on Old Style and New Style dates, so obviously there is plenty of information, but that information does not belong in this article. --Nike 21:57, 4 October 2005 (UTC)[reply]

The problem of "not specific enough" is very common on Wikipedia and there is a standard solution used all the time: disambiguation. However, disambiguation is only used and needed where two or more articles of a given title actually exist. When there is not, I've seen various editors removing the superfluous part in parentheses and renaming.

"Susan Smith" might be perfectly specific enough if there is no other encyclopedic Susan Smith or if she's the most notorious Susan Smith and the rest can be listed on a disambiguation page. If if turns out that's not specific enough, "Susan Smith (murderer)" is a little more specific, and if there are two Susan Smiths who killed, then we would get as minimally specific as necessary with "Susan Smith (South Carolina murderer)" etc. Or to cite actual cases, there are two astronomers named Paul Wild and two people connected with astronomy/space exploration named William H. Pickering.

In this case, I'd argue that the astronomical usage of "Julian year" predominates because it's in actual current usage and the Julian calendar is not. And we don't have separate Julian month and Julian day of the month articles either, all of these are simply discussed in subsections of Julian calendar, so it's uncertain whether a separate article is warranted. If that article mostly discusses what day is considered the first day of the year, then "Julian year" is perhaps not the clearest title for it. -- Curps 04:11, 5 October 2005 (UTC)[reply]