Why do Oracle dates go only up to 4712 A.D. is there some technical reason for such a specific date
mosene
Deepak Surana
mosene wrote:
> why 4712 and not something else?
--
Deepak Surana, BT Plc.
Direct : + 44-181-5876433 GMT
e-mail : deepak...@bt.com
Michael S. Abbey
>why 4712 and not something else?
It's based on some internal algorithm which factors in the current
temperature (in Kelvin), the seconds since midnight and the dimensions
of a sphere using Calcutta and Bombay as centres. Then the system date
minus the square root of -34 is dissolved in the result, giving 4712.
Hope this helps ...
+-----------------------------
+ Michael S. Abbey
+ Co-author of 7 works in the
+ Oracle Press series
+-----------------------------
Alan Shein
P(e)=DB2
where DB=68.644009 (the number of bytes of overhead in an average row.), so
DB2=~4712.
Michael S. Abbey <ab...@pythian.com> wrote in message
news:38399b4c....@news.magma.ca...
Paul Q
Hail Caeser.
Astronomical Julian Days
Although Joseph Justus Scaliger was, as noted above, one of the founders of
the science of chronology, it seems he did not invent the Julian day number
system. Its inventor was the astronomer John W. F. Herschel. Lance Latham
writes:
"It remained, however, for the astronomer John F. Herschel to turn this idea
[of Scaliger's] into a complete time system, rather than a method of
relating years. In 1849, Herschel published Outlines of Astronomy and
explained the idea of extending Scaliger's concept to days." — The Standard
C Date/Time Library, p.42.
Following Herschel's lead astronomers adopted this system and took noon
GMT -4712-01-01 J (January 1st, 4713 B.C.) as their zero point. (Note that
4713 B.C. is the year -4712 according to the astronomical year numbering.)
For astronomers a Julian day begins at noon and runs until the next noon (so
that the nighttime falls conveniently within one "day", unless they are
making their observations in a place such as Australia). Thus they defined
the Julian day number of a day as the number of days (or part of a day)
elapsed since noon GMT (or more exactly, UT) on January 1st, 4713 B.C., in
the Proleptic Julian Calendar.
Thus the Julian day number of noon GMT on -4712-01-01 (Julian), or more
casually, the Julian day number of -4712-01-01 itself, is 0. The Julian day
number of 1996-03-31 is 2,450,174 — meaning that on 1996-03-31 2,450,174
days had elapsed since -4712-01-01 (or more exactly, that at noon on
1996-03-31 2,450,174 days had elapsed since noon on -4712-01-01).
A decimal component may be used, so that JD 0.5 is the midnight point
separating -4712-01-01 J and -4712-01-02 J, JD 1.25 is 6 p.m. on -4712-01-02
J, and so on.
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mosene wrote in message ...
Van Messner
Deepak Surana <dsu...@mahindrabt.com> wrote in message
news:38398C06...@mahindrabt.com...
> the limit is 9999 not 4712 (must be a documentation bug ?)
>
> mosene wrote:
>
> > why 4712 and not something else?
>
RyuO
earlier release it is +- 4712.
I think the reason for the change is to give Oracle Consulting enough
time to finish some government projects :)
In article <38398C06...@mahindrabt.com>,
Deepak Surana <dsu...@mahindrabt.com> wrote:
> the limit is 9999 not 4712 (must be a documentation bug ?)
>
> mosene wrote:
>
> > why 4712 and not something else?
>
> --
> Deepak Surana, BT Plc.
> Direct : + 44-181-5876433 GMT
> e-mail : deepak...@bt.com
>
>
Sent via Deja.com http://www.deja.com/
Before you buy.
Fred Petillo
Joseph Justus Scaliger (born 1540-08-05 J in Agen, France, died
1609-01-21 J in Leiden, Holland), who during his life immersed himself in Greek,
Latin, Persian and Jewish literature, and who was one of the founders of the
science of chronology. Scaliger's invention was not the system of Julian days, but
rather the so-called Julian period.
Scaliger combined three traditionally recognized temporal cycles of 28, 19 and 15
years to obtain a great cycle, the Scaliger cycle, or Julian period, of
7980 years (7980 is the least common multiple of 28, 19 and 15). According to the
Encyclopedia Brittanica:
"The length of 7,980 years was chosen as the product of 28 times 19 times 15;
these, respectively, are the numbers of years in the so-called
solar cycle of the Julian calendar in which dates recur on the same days of the
week; the lunar or Metonic cycle, after which the phases of the
Moon recur on a particular day in the solar year, or year of the seasons; and
the cycle of indiction, originally a schedule of periodic taxes or
government requisitions in ancient Rome."
According to some accounts Scaliger named his Julian period after his father, Julius
Scaliger. However in his De Emandatione Temporum (Geneva, 1629)
Scaliger says: "Julianam vocauimus, quia ad annum Julianum accommodata ..."
(translated by R. L. Reese et al. (3) as "We have termed it Julian because it
fits the Julian year ...").
Regarding the Julian period the U.S. Naval Observatory has this to say:
"In the 16th century Joseph Justus Scaliger tried to resolve the patchwork of
historical eras by placing everything on a single system. Not being
ready to deal with negative year counts, he sought an initial epoch in advance
of any historical record. His approach was numerological and
utilized three calendrical cycles: the 28-year solar cycle, the 19-year cycle of
Golden Numbers, and the 15-year indiction cycle. The solar cycle
is the period after which week days and calendar dates repeat in the Julian
calendar. The cycle of Golden Numbers is the period after which
moon phases repeat (approximately) on the same calendar dates. The indiction
cycle was a Roman tax cycle of unknown origin. Therefore,
Scaliger could characterize a year by the combination of numbers (S,G,I), where
S runs from 1 through 28, G from 1 through 19, and I from 1
through 15. Scaliger first stated that a given combination would recur after
7980 (= 28 x 19 x 15) years. He called this a Julian cycle because it
was based on the Julian calendar. Scaliger knew that the year of Christ's birth
(as determined by Dionysius Exiguus) was characterized by the
number 9 of the solar cycle, by Golden Number 1, and by number 3 of the
indiction cycle, or (9,1,3). Then Scaliger chose as this initial epoch
the year characterized by (1,1,1) and determined that (9,1,3) was year 4713 of
his chronological era [and thus that year (1,1,1) was 4713 B.C].
Scaliger's initial epoch was later to be adopted as the initial epoch for the
Julian day numbers." — The 21st Century and the 3rd Millennium
It turns out, however, that the Julian period was discovered by others before
Scaliger. Roger, Bishop of Hereford, discusses the three cycles used by Scaliger
in his Compotus (written in 1176 CE) and states that "these three ... do not come
together at one point for 7980 years" (see (5)), although he does not
identify the year (4713 B.C.) of their coincidence. Furthermore, according to R. L.
Reese et al. (6):
"A 12th-century manuscript indicates that the 7980-year period was used
explicitly for calendrical purposes by an earlier Bishop of Hereford,
Robert de Losinga, in the year A.D. 1086, almost a century before the Bishop of
Hereford named Roger. ... Robert de Losinga combines the
solar, lunar and indiction cycles into a "great cycle [magnum ciclum]" of 7980
years ... Thus the manuscript by Robert de Losinga places the
earliest known use of the Julian period in the year A.D. 1086."
The first Julian period began with Year 1 on -4712-01-01 (Julian) and will end after
7980 years on 3267-12-31 (Julian), which is 3268-01-22 (Gregorian).
3268-01-01 J is the first day of Year 1 of the next Julian period
Cheers,
Fred