[Coco] Julian Date

[Gene Heskett]

On Sunday 21 May 2017 02:12:08 Arthur Flexser wrote:

> One might also point out that the subject line is misleading, as the
> rule you're talking about describes the present-day (since 1582)
> Gregorian calendar, not the Julian one, as correctly alluded to by
> William.  The Gregorian calendar modified the Julian one by
> introducing the rule that made only every fourth century year a leap
> year, bringing the calendar year into closer correspondence with the
> astronomical solar year so that seasons stay in the same place from
> year to year, with only an occasional leap second needed to keep it
> all in sync.
>
> 1 average year (Julian) = 365.25 days
> 1 average year (Gregorian) = 365.2425 days
> 1 solar year = 365.24217 days
>
> Art

What amazes me about all this is that in 1582, Pope Gregory had such 
mathematicians and methods of measurement to be able to determine this 
with the accuracy needed to have seasons stable to a few minutes in any 
individual year, with the accuracy we still enjoy 435 years later, and 
will have yet in 10,000 AD, if we, or yellowstone don't sterilize much 
of the planet. With an occasional leap second thrown in.  This will 
become more frequent as the century's go by since the earth is 
still "cleaning out" its orbit, taking on quite a few tons of sand and 
smaller sized material a day, all of which has to be adjusted from a 
rotationally neutral mass to the rotational speed of the planet.  This 
takes energy, with the net effect of making our "day" longer, so the 
need for the leap second will come ever more frequently. This calendar 
will serve for quite some time yet.  The accretion of this mass also 
slows our orbital speed, lowering our orbit over the eons. This will 
have a heating effect, but of far less magnitude than the brightening of 
our home star as it approaches the end of its life, projected as about 5 
billion years yet.

At the moment, what we are doing to the planets albedo with our air 
pollution, is warming the plant, melting the polar caps and raising sea 
levels is a far more worrysome thing. I fear that this will effect 
things and will do much to depopulate it until the resources available 
once again match our useage.

> On Sun, May 21, 2017 at 1:26 AM, Gene Heskett <gheskett at shentel.net> 
wrote:
> > On Saturday 20 May 2017 23:48:59 William Astle wrote:
> > > On 2017-05-20 05:10 PM, Gene Heskett wrote:
> > > > Basically if the year is divisible by 4 its a leap year UNLESS
> > > > the date is divisible by 400 without a remainder, then it is not
> > > > a leap year. 2000 was not a leap year. 2400 will not be a leap
> > > > year.  The C manual uses the mod(year,4) or mod(year,400) to
> > > > determine this IIRC.
> > >
> > > Lest this leave people with an inaccurate understanding of the
> > > Gregorian calendar, I think I should mention that Gene doesn't
> > > quite have this right.
> > >
> > > The actual rule is: A year is a leap year if it is divisible by 4
> > > but is not divisible by 100. Additionally, if the year is
> > > divisible by 400, it is a leap year.
> > >
> > > Note that 2000 *was* a leap year. 1900 wasn't and 2100 will not be
> > > but 2400 will be.
> >
> > Ya caught me out on that one, William. I don't even have to pull one
> > of my copies of K&R (I have both) down to double check.  Can I blame
> > it on oldtimers? At 82, the wet ram I am finding is not quite as
> > photographic as it once was.
> >
> > Cheers, Gene Heskett
> > --
> > "There are four boxes to be used in defense of liberty:
> >  soap, ballot, jury, and ammo. Please use in that order."
> > -Ed Howdershelt (Author)
> > Genes Web page <http://geneslinuxbox.net:6309/gene>
> >
> > --
> > Coco mailing list
> > Coco at maltedmedia.com
> > https://pairlist5.pair.net/mailman/listinfo/coco


Cheers, Gene Heskett
-- 
"There are four boxes to be used in defense of liberty:
 soap, ballot, jury, and ammo. Please use in that order."
-Ed Howdershelt (Author)
Genes Web page <http://geneslinuxbox.net:6309/gene>