[LEAPSECS] alternative to smearing

Wed Jan 11 09:39:49 EST 2017

On Wed Jan 11 05:32:05 EST 2017, Clive D.W. Feather wrote:

"Why [GDs]?"

Because I want the proleptic gregorian calendar to represent Anno Domini.

"Why [the zero point in time must be the same for both the daily, and the
annual continuous timescale]?"

I think there is something special about Anno Domini. As opposed to Anno
Mundi, that begin with the creation, and in principle has no time before
the creation, Anno Domini begin with the incarnation, and has infinite time
both before, and after the incarnation. Forgive me for elaborating on this,
on this mailing list, but since you asked I feel allowed to answer.

The chronology of Anno Domini is not quite settled. Dionysius (470-544)
used the incarnation as the beginning of his easter tables, and since then
the church has used AD. Nevertheless, the time of the incarnation is not
quite settled. As Newcomb points out, the Christian era has no year zero.
He writes:

"To avoid the inconvenience thus arising astronomers measure the years from
a zero epoch one year earlier than the birth of Christ ; that is, they
place a year before the year 1, and measure from its beginning."
(Compendium, 1906, p. 123)

Dionysius actually used zero (nulla) in his easter tables, but at least
since Bede (672-735) the church has followed the convention, not to use a
year zero.

I see the proleptic gregorian calendar, represented by ISO 8601, and the
GDs I propose, as a scientific way to settle the time of the incarnation.
The incarnation was not only the birth of Christ. The incarnation was a
period, from conception to ascension, when the only begotten son of God the
Lord appeared "in flesh", and that period I want to see symbolized by the
year zero - "the year of the incarnation". The conception, by the Holy
Spirit, shall be said to have happened sometime in the year zero, and
Christmas shall be a yearly remembrance of the incarnation.

I hope the whole church one day will celebrate Christmas on the same day.
For the whole church to celebrate Christmas on the same day, it is
necessary that the whole church follow the same calendar. I don't like to
see the east celebrate Christmas according to the julian calendar, and I
would like to see the east follow the gregorian calendar. Somehow I believe
the proleptic gregorian calendar, and the GDs I propose, is the best way to
settle the time of the incarnation, and unite east and west around the same
calendar.

If you don't care about Christ, and the church, I can understand why you
treat all timescales alike. But if you really care about the fundamental
timescale of science and society, then I don't see how you can ignore the
time of the incarnation.

-Preben

2017-01-11 11:32 GMT+01:00 Clive D.W. Feather <clive at davros.org>:

> Preben Nrager said:
> > Let's say Newcomb envisions negative JDs, and astronomy thus uses the JD
> > system. Astronomy then have two different "eternal" timescales, with two
> > different starting points for zero: The one is the proleptic gregorian
> > calendar, represented by ISO 8601, with the starting year zero, and the
> > other the JD system, with the starting day zero.
>
> Yes. So what?
>
> > I understand the need in astronomy, and computer science, for a
> continuous
> > timescale, and I understand that continuous days, and fractions of days,
> is
> > better suited that need, than continuous
> > years:months:days:hours:minutes:seconds. But I don't understand how
> > astronomy can cope with two different starting points for zero.
>
> Very simply. If I write "JD 12345678" I mean a specific day (pace the
> issues about which definition of "day" is being used). If I write
> "1234-05-26 PG" (or whatever abbreviation is used) I mean a different
> specific day. Conversion between the two is a simple algorithm.
>
> > The
> > beginning of time must be a beginning in time,
>
> We aren't talking about "the beginning of time". We're talking about the
> arbitrary zero point for a date labelling system. There is absolutely no
> problem with two systems having two zero points.
>
> For that matter, the actual definition of year numbers in ISO 8601 is - or
> was last time I read it - that year 1875 is the year that the Treaty of the
> Metre is signed. In other words, it's not even defined by where zero is!
>
> > and I don't see how
> > astronomy can have a day zero, that is different from the year zero. The
> > zero point in time must somehow be the same for both the daily, and the
> > annual timescale.
>
> The reference point of the Celsius temperature scale is the melting point
> of pure H2O at an arbitrary atmospheric pressure whose value I forget. The
> reference point of the Kelvin temperature scale is the thermodynamic
> minimum possible temperature ("absolute zero"). Nothing stops people using
> both even though they have different zero points. And that's without
> mentioning Farenheit, Rankine, Romer, Newton, Delisle, Reaumur, Leiden,
> Wedgwood, and Gas Marks.
>
> Time is no different. Provided that we know the conversion algorithm, there
> is absolutely no problem with having multiple systems. See the book
> "Calendric Calculations" for further details.
>
> > The way I see the JD system being used in astronomy, it is as the
> > fundamental timescale. The number of JD is related to the days in either
> > the julian or the gregorian calendar, but the proleptic gregorian
> calendar,
> > with year zero, is not really being used. I don't know if that is because
> > Christmas day (December 24/25), and other important days, are not the
> same
> > JD in the julian, and the proleptic gregorian calendar,
>
> 1234-12-25 Julian and 1234-12-25 proleptic Gregorian are different days.
> Just as 2017-12-25 Julian and 2017-12-25 Gregorian will be different days.
> So what?
>
> > but either way, the
> > zero point in time must be the same for both the daily, and the annual
> > continuous timescale.
>
> Why?
>
> > I propose to reform the JD system with a new system of proleptic
> gregorian
> > days GD. The proleptic gregorian calendar, with year zero, shall be the
> > fundamental timescale, and in that calendar each year has either 365 or
> 366
> > days, in accordance with the gregorian leap year rules. Year 0 is a leap
> > year.
> >
> >
> > The new system of GD shall like JD count the days from noon to noon. But
> > the zero day shall not be JD:0. The zero day of GD shall be the day from
> > -0001-12-31T12:00 to 0000-01-01T12:00. That day is JD:17210159, so my
> > reform will be the removal of 17210158 days from JD, to create GD.
>
> So your GDs are just JD minus 17210158? That shows that you can cope with
> two different zero point with no trouble.
>
> > With the new timescale I propose, negative years and negative days will
> > always be the same,
>
> Okay.
>
> > and that I think is important.
>
> Why?
>
> Anyone who's dealt with AD, AM, and AH dates knows that a date can be
> positive in one system and negative in another. That's not a problem -
> there's nothing magical about negative year numbers.
>
> You might just as well argue that we should use LCDs, where the zero point
> is the Mayan Long Count date 0.0.0.0.0 (-3113-08-11 PG).
>
> --
> Clive D.W. Feather          | If you lie to the compiler,
> Email: clive at davros.org     | it will get its revenge.
> Web: http://www.davros.org  |   - Henry Spencer
> Mobile: +44 7973 377646
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