On 17-Nov-2011 14:55 , John Yeung wrote:
This is my point exactly. There is no reason for that *format*
to be called Julian, because there is no relationship between
that format and any variation on the Julian date system. Even
the astronomical Julian date system (a) uses the Julian calendar,
and (b) is a number of days from a single fixed point in all of
time, not from the beginning of EACH year.
I agree succumbing to common vernacular is sometimes problematic for
promoting proper understanding. But I also suppose IBM need not be so
pedantic as the French might be with protecting their language, if
solely in some ill-conceived attempt to correct a misrepresentation in
naming already adopted by the commoners who are rightly outside the
control of standards minders. I doubt the _ordinal_ date format will
become the common term used to describe a format showing the number of
days in a year, even if IBM were to "correct" its own references; MS
obviously has not cured people of the misuse, and their .NET refers to
Ordinal versus Julian for that format.
Regardless, the IBM InfoCenter accepts feedback, and literally anyone
with web\browser access has the option to nudge them to use the
"correct" terminology in their docs.
Did Julius Caesar express dates as a year and a number of days from
the beginning of that year? No. He used 12 months, and days within
the month, just like we do today. So where does "Julian format" come
from?
I personally have never had any concern for the reference to the
YY/DDD format as "Julian". First, because I only learned of the term
"Ordinal" for a date format, years after adopting the already common
term "Julian". And second, because "Julian" as I had originally
learned, was a means to represent a number of [partial] days since a
base-date, similarly how in any one year the "Ordinal" happens to
represent effectively the number of days since the zero-hour of any
given year in a similar manner.
I would extend no more effort to argue against the use of "Julian"
for that format than I would against the use of "century" to describe
the 1900s as contrasted with what many claim would more correctly be
from 1901 until the end of 2000. The term century means 100 years,
irrespective of the start... so I can easily accept that the term Julian
can refer to a number of days counted from any point, irrespective of
start... and that is IMO effectively what YYYY/DDD portrays.
So perhaps whoever originated the ordinal date format, first referred
to it as Julian because of a perceived conceptual parallel. And perhaps
the more appropriate name of Ordinal only came about later.?
First of all, there would be no useful reason to support anything
other than the Gregorian calendar. It's what the entire world uses,
at least when interacting internationally. (There are religious,
cultural, and local calendar systems that may be used internally by
those religions, cultures, or localities.)
I can not claim to know what the entire world uses, but I do know of
Era dates still being used regularly\solely in the recent past. A major
application had no input nor output of any Gregorian date values for the
UI, and only Era dates were stored in the database. While I am
unfamiliar with any specific scenario, I was made aware of indications
that a religious calendar was being used similarly. In each case, that
the rest of the world insists they must deal with Gregorian calendar
dates is best I can tell, just a temporary force\pressure; i.e. little
different than English seeming to remain globally prominent, which could
easily change based solely on the percentage of users.? International
standards are no more permanent than stone ;-)
The MI has support for Gregorian, Julian, and Era calendar types
AFaIK. I seem to recall there was obvious capability for expanding to
support many more calendars; from the MI DDATs I think. Sometimes a
calendar may just be a simple offset from Gregorian dates, or they may
require [or at least better be implemented with] something completely
different.
Second, I'm not completely sure what you mean by skipped/missing days.
Are you referring to the point at which England switched from the
Julian calendar to the Gregorian, and thus had to enact a one-time
correction?
No. As a reflection of original creation\adoption by the pope, not a
reflection of any particular later adoptions. As I understand, the
creator of the Gregorian calendar [named for and commissioned by, but
not made by, a Pope Gregory], eliminated several days in the 1500s to
enable the new calendar to reflect the appropriate\corrected day of a
religious rite while apparently also giving recognition of days already
passed.?
Unless you are a historian and your data actually uses dates from
that time (and keep in mind that different areas of the world
switched to Gregorian at different times; Russia was still using the
Julian calendar until 1918!), it really only makes sense to do all
calculations as if the Gregorian calendar had always been in effect.
(And this is what the IBM-supplied functions do.)
Agreed. In computing we normally choose to assume consecutive dates
back to a year-one, to a year-zero, or perhaps even further back. That
is all done by extrapolation however. If the original Gregorian
calendar had indeed omitted several days for the convenience of tracking
already recognized past dates, then they can [presently] hardly fault us
for ignoring\overlooking that unnecessary complexity several hundred
years later. :-)
I alluded to the missing days to emphasize that even what is claimed
to represent the Gregorian calendar, is possibly inaccurate. If one
were consistent, then a desire for complete accuracy in the use of the
term Julian should probably apply equally to the use of the term
Gregorian. Insistence on strict recognition of there being no year-zero
for instance, ignores an ambiguity whereby the origin of the Gregorian
calendar is presumed to be within +\- perhaps a decade of the intended
inception date.
I will say this: I have seen a lot of home-grown date code that
calculates as if the Julian calendar were in effect! (Specifically,
any code that assumes *every* 4th year is a leap year is effectively
using the Julian calendar, and not the Gregorian calendar.)
Sad; though such a calculation can be valid across four hundred
years.? But there is a lot of bad code, hardly limited to date
processing ;-)
Regards, Chuck
midrange.com
