A Proposed Usage of 'Common Era' (CE)

[Karl Palmen]

Dear Calendar People

Peter Meyer of Hermetic Systems http://www.hermetic.ch/index.php who is also an occasional member of this list uses the Common Era (CE) year numbering system in a specific way, which distinguishes it from AD/BC and may encourage use of astronomical year numbering along with the proleptic Gregorian calendar. In this specific way,

(1)     Common Era (CE) is used only with astronomical year numbering, which has year 1 preceded by year 0 and negative numbered years. There is no BCE.

(2)     Whenever a date is used with a common era year number,  it is always in the (proleptic) Gregorian calendar. Dates before the adoption of the Gregorian calendar are always expressed as though the Gregorian calendar were already in use rather than in the Julian calendar.

The calendar resulting from this is called the Common Era Calendar (rather than Proleptic Gregorian Calendar with Astronomical Year Numbering in Common Era).

Comments from calendar people are welcome.

See http://www.hermetic.ch/cal_stud/astronomical_year_numbering.htm for more details.

Karl

10(13(19

--
Scanned by iCritical.

[Tom Peters-6]

Op 7-okt-2009, om 14:00 heeft Karl Palmen het volgende geschreven:

> Dear Calendar People
>
> Peter Meyer of Hermetic Systems http://www.hermetic.ch/index.php 
> who is also an occasional member of this list uses the Common Era  
> (CE) year numbering system in a specific way, which distinguishes  
> it from AD/BC and may encourage use of astronomical year numbering  
> along with the proleptic Gregorian calendar. In this specific way,
>
> (1)     Common Era (CE) is used only with astronomical year  
> numbering, which has year 1 preceded by year 0 and negative  
> numbered years. There is no BCE.
>
> (2)     Whenever a date is used with a common era year number,  it  
> is always in the (proleptic) Gregorian calendar. Dates before the  
> adoption of the Gregorian calendar are always expressed as though  
> the Gregorian calendar were already in use rather than in the  
> Julian calendar.
>
>
> The calendar resulting from this is called the Common Era Calendar  
> (rather than Proleptic Gregorian Calendar with Astronomical Year  
> Numbering in Common Era).
>
> Comments from calendar people are welcome.
>

   I find the use of the proleptic Gregorian Calendar A Very Bad  
Idea.  It has had some popularity among students of pre-Columbian  
cultures, presumably on the false assumption that Gregorian dates  
would be stable in the seasons across the ages, at least better than  
the Julian calendar.  It has also been adopted bij Reingold &  
Dershowitz in their Calendrical Calculations, and they even  
introduced their own day numbering from the epoch in Gregorian  
calendar - the benefits of both still escape me.

   The big problem with proleptic Gregorian dates is, that for much  
of history, it introduces a different but very similar looking date  
for days that already had a Julian date actually assigned to them at  
the time.  1 May 1400 has always been called 1 May 1400, and calling  
it 10 May 1400 can only lead to confusion, without any added benefit.
   The proleptic Julian calendar does not have this problem to any  
appreciable extent, because there was no competing widespread  
calendar, and in so far as there was  - e.g. the hellenized Egyptian  
calendar that astronomers used - its dates can not be confused with  
Julian dates.

   So proleptic Julian calendar: yes; proleptic Gregorian calendar: NO!
--
Tom Peters

[Mark J. Reed]

The benefit lies in the lack of discontinuities all the way to the
present day, with a resulting ease of calculation, plus the fact that
the resulting label for a day is unambiguous within the system.  If
you haven't established up front what calendar is in use, then while 1
May 1400 may be unambiguous,1 May 1600 is not: it can refer to either
a Monday or the Thursday ten days later, depending on locale.  When
using dates of this form, you always have to specify whether you mean
Julian or Gregorian; at least using a single calendar for all time
means you only have to specify it once.  With your proposal you would
have to specify the calendar for every date, or else establish a
particular switchover - but historically that's dependent on
geography.

There are lots of complexities involved in decoding dates from
historical documents.   But there needn't be any such complexities for
a modern author specifying dates in the past.

And I don't understand the contemporaneous usage argument. Going back
before about 600 CE, the use of CE years is ahistorical.  Before 8 CE,
retrojected Julian dates no longer match contemporary reality, and of
course before 46 BCE are no less  proleptic than the Gregorian...

--
Mark J. Reed <markjreed@...>

[Karl Palmen]

Dear Mark and Calendar People

For dates before the adoption of the Gregorian Calendar, Peter's proposal would use AD/BC for (proleptic) Julian calendar dates and CE with astronomical year numbering for proleptic Gregorian calendar, which he calls the Common Era Calendar. So just two letters would specify the calendar.

The proposal would have to abolish BCE and the use of the (proleptic) Julian calendar with CE dates, but not AD/BC dates.

Karl

10(13(19 till noon

-----Original Message-----
From: East Carolina University Calendar discussion List [mailto:CALNDR-L@...] On Behalf Of Mark J. Reed
Sent: 07 October 2009 21:08
To: CALNDR-L@...
Subject: Re: A Proposed Usage of 'Common Era' (CE)

The benefit lies in the lack of discontinuities all the way to the
present day, with a resulting ease of calculation, plus the fact that
the resulting label for a day is unambiguous within the system.  If
you haven't established up front what calendar is in use, then while 1
May 1400 may be unambiguous,1 May 1600 is not: it can refer to either
a Monday or the Thursday ten days later, depending on locale.  When
using dates of this form, you always have to specify whether you mean
Julian or Gregorian; at least using a single calendar for all time
means you only have to specify it once.  With your proposal you would
have to specify the calendar for every date, or else establish a
particular switchover - but historically that's dependent on
geography.

There are lots of complexities involved in decoding dates from
historical documents.   But there needn't be any such complexities for
a modern author specifying dates in the past.

And I don't understand the contemporaneous usage argument. Going back
before about 600 CE, the use of CE years is ahistorical.  Before 8 CE,
retrojected Julian dates no longer match contemporary reality, and of
course before 46 BCE are no less  proleptic than the Gregorian...

--
Mark J. Reed <markjreed@...>

[Peter Meyer-3]

Dear CALNDR-L members,

Karl informed me that he had started this thread
(after previous discussion off-list), so I thought
I'd better check back in.

Thanks to Mark Reed and Tom Peters for their comments.
I should clarify a couple of points, since even Karl
has not got it quite right.

'A' calendar can have more than one system of dates
(a.k.a. a date notation) associated with it.  Since a
calendar designation such as 'BC' is part of a date
such as '200-01-01 BC', a notation which use 'BCE'
is not the same as one which uses 'BC', even though
the two notations are isomorphic.

In my calendar software and calendar articles I use 'CE'
to denote a system of dates, for use with the proleptic
Gregorian Calendar (GC both forwards and backwards from
1582-10-15), which uses the astronomical year numbering
system.  This is a date notation obviously different
from that commonly used (with AD/BC calendar designation).

What I have proposed is to use the term 'Common Era Calendar'
to refer to what I have described in the previous paragraph.
It is a 3-word term which means the same as "The proleptic
Gregorian Calendar with astronomical year numbering and which
distinguishes dates in this system from those in others by
use of the designation 'CE'".  This is obviously too long
to be used always when referring to the calendar (with the
specific date notation) described above.

So to be clear, I propose 'CE' as the date designator
for a system of dates (i.e., a date notation).  

Karl has not got it right when he said:

>For dates before the adoption of the Gregorian Calendar,
>Peter's proposal would use AD/BC for (proleptic) Julian calendar
>dates and CE with astronomical year numbering for proleptic
>Gregorian calendar,

No.  I propose to use 'JC' for dates in the proleptic Julian
Calendar with astronomical year numbering.  Thus 'CE' dates
and 'JC' dates would be analogous, with the former designating
dates in the proleptic Gregorian Calendar and the latter
designating dates in the proleptic Julian Calendar.
This is mentioned, though perhaps not clearly enough,
in my brief note on this subject at
http://www.hermetic.ch/cal_stud/astronomical_year_numbering.htm

These proposals are mainly directed toward calendrical
scientists.  Or in other words, I propose these date notations
as standards for use in technical chronology.  Those who
are not scholars in this field may, of course, prefer to
remain with their AD/BC date notations or whatever.

For both calendrical scientists and others there is a need
for software to convert between these 'CE' and 'JC' dates
(which use astronomical year numbering) with negative years
and dates using BC/BCE/v.Chr.  I am now working on a program
to do this, which I shall make freely available to list members.

Regards,
Peter Meyer
http://www.hermetic.ch

[Brillig]

For disambiguation, day of week could be appended. For example, 1600-01-06, Thursday, is unambiguous, even though Gregorian or Julian is not specified. Dates thus specified would be ambiguous only for periods of time when the drift between Gregorian and Julian is exactly a multiple of 7 days. No such day occurred when both calendars were in use. Specifying a weekday for years before year 1 will also serve as a parity check to determine if there is a zero year implied.

A DOW supplement would not be helpful if it were a number, since it is not clear if a 0..6 or 1..7 scheme is used or what day starts the week. That means it is language specific.

Victor

On Thu, Oct 8, 2009 at 10:26 AM, Peter Meyer <pm@...> wrote:

Dear CALNDR-L members,

Karl informed me that he had started this thread
(after previous discussion off-list), so I thought
I'd better check back in.

Thanks to Mark Reed and Tom Peters for their comments.
I should clarify a couple of points, since even Karl
has not got it quite right.

'A' calendar can have more than one system of dates
(a.k.a. a date notation) associated with it.  Since a
calendar designation such as 'BC' is part of a date
such as '200-01-01 BC', a notation which use 'BCE'
is not the same as one which uses 'BC', even though
the two notations are isomorphic.

In my calendar software and calendar articles I use 'CE'
to denote a system of dates, for use with the proleptic
Gregorian Calendar (GC both forwards and backwards from
1582-10-15), which uses the astronomical year numbering
system.  This is a date notation obviously different
from that commonly used (with AD/BC calendar designation).

What I have proposed is to use the term 'Common Era Calendar'
to refer to what I have described in the previous paragraph.
It is a 3-word term which means the same as "The proleptic
Gregorian Calendar with astronomical year numbering and which
distinguishes dates in this system from those in others by
use of the designation 'CE'".  This is obviously too long
to be used always when referring to the calendar (with the
specific date notation) described above.

So to be clear, I propose 'CE' as the date designator
for a system of dates (i.e., a date notation).

Karl has not got it right when he said:

>For dates before the adoption of the Gregorian Calendar,
>Peter's proposal would use AD/BC for (proleptic) Julian calendar
>dates and CE with astronomical year numbering for proleptic
>Gregorian calendar,

No.  I propose to use 'JC' for dates in the proleptic Julian
Calendar with astronomical year numbering.  Thus 'CE' dates
and 'JC' dates would be analogous, with the former designating
dates in the proleptic Gregorian Calendar and the latter
designating dates in the proleptic Julian Calendar.
This is mentioned, though perhaps not clearly enough,
in my brief note on this subject at

http://www.hermetic.ch/cal_stud/astronomical_year_numbering.htm

These proposals are mainly directed toward calendrical
scientists.  Or in other words, I propose these date notations
as standards for use in technical chronology.  Those who
are not scholars in this field may, of course, prefer to
remain with their AD/BC date notations or whatever.

For both calendrical scientists and others there is a need
for software to convert between these 'CE' and 'JC' dates
(which use astronomical year numbering) with negative years
and dates using BC/BCE/v.Chr.  I am now working on a program
to do this, which I shall make freely available to list members.

Regards,
Peter Meyer
http://www.hermetic.ch

[Tom Peters-6]

Op 7-okt-2009, om 22:07 heeft Mark J. Reed het volgende geschreven:

> The benefit lies in the lack of discontinuities all the way to the
> present day, with a resulting ease of calculation, plus the fact that
> the resulting label for a day is unambiguous within the system.  If
> you haven't established up front what calendar is in use, then while 1
> May 1400 may be unambiguous,1 May 1600 is not: it can refer to either
> a Monday or the Thursday ten days later, depending on locale.  When
> using dates of this form, you always have to specify whether you mean
> Julian or Gregorian; at least using a single calendar for all time
> means you only have to specify it once.  With your proposal you would
> have to specify the calendar for every date, or else establish a
> particular switchover - but historically that's dependent on
> geography.

15 Oct 1582 seems the proper switchover date for a universal  
calendar.  After that, it is just local convention to use Julian.

> There are lots of complexities involved in decoding dates from
> historical documents.   But there needn't be any such complexities for
> a modern author specifying dates in the past.
>
> And I don't understand the contemporaneous usage argument. Going back
> before about 600 CE, the use of CE years is ahistorical.  Before 8 CE,
> retrojected Julian dates no longer match contemporary reality, and of
> course before 46 BCE are no less  proleptic than the Gregorian...

Era and year count are a convention somewhat distinct from the annual  
calendar proper (start of year, division over months).  "CE"  can be  
read as "Common Era" or "Conventional Era", not just "Christian  
Era".  Specifying years from any epoch was universally impopular  
before Bede (8th cy.) so there is no universally accepted competitor  
before that time and it is fine to a-historically project the CE  
count into the past.

But if you want a single continuous calendar, then it should be  
Julian, not Gregorian.  In that case more actual historic dates will  
be correct (8 AD to 1582 AD) than Gregorian (1917..) for a long time.
   Before 8 AD calendars were a universal mess anyway so I see no  
competitor for the proleptic Julian calendar.  Unless you want to re-
introduce the older and even more regular hellenistic/Egyptian annus  
vagus, or the Mayan haab, or the Sumerian 360-day administrative count.
     The Julian calendar may not follow the mean tropical year nor  
mean spring aequinox year nor sidereal year very accurately, but  
neither does the Gregorian year, and the latter's intercalation  
scheme is unnecessarily complex and non-optimal as discussed many  
times in this list.  So for simplicity and continuity, the Julian  
calendar is the one of choice over the Gregorian in my opinion.
--
Tom Peters

[Mark J. Reed]

Except for the minor detail that the Gregorian is in universal current
use, so dates for the present and last few centuries won't match.
Intentionally introducing a divergence from the system of record going
forward seems unwise. At least historical dates only need to be
translated once,...

On Saturday, October 10, 2009, Tom Peters <tpeters@...> wrote:

> Op 7-okt-2009, om 22:07 heeft Mark J. Reed het volgende geschreven:
>
>
> The benefit lies in the lack of discontinuities all the way to the
> present day, with a resulting ease of calculation, plus the fact that
> the resulting label for a day is unambiguous within the system.  If
> you haven't established up front what calendar is in use, then while 1
> May 1400 may be unambiguous,1 May 1600 is not: it can refer to either
> a Monday or the Thursday ten days later, depending on locale.  When
> using dates of this form, you always have to specify whether you mean
> Julian or Gregorian; at least using a single calendar for all time
> means you only have to specify it once.  With your proposal you would
> have to specify the calendar for every date, or else establish a
> particular switchover - but historically that's dependent on
> geography.
>
>
> 15 Oct 1582 seems the proper switchover date for a universal calendar.  After that, it is just local convention to use Julian.
>
>
> There are lots of complexities involved in decoding dates from
> historical documents.   But there needn't be any such complexities for
> a modern author specifying dates in the past.
>
> And I don't understand the contemporaneous usage argument. Going back
> before about 600 CE, the use of CE years is ahistorical.  Before 8 CE,
> retrojected Julian dates no longer match contemporary reality, and of
> course before 46 BCE are no less  proleptic than the Gregorian...
>
>
> Era and year count are a convention somewhat distinct from the annual calendar proper (start of year, division over months).  "CE"  can be read as "Common Era" or "Conventional Era", not just "Christian Era".  Specifying years from any epoch was universally impopular before Bede (8th cy.) so there is no universally accepted competitor before that time and it is fine to a-historically project the CE count into the past.
>
> But if you want a single continuous calendar, then it should be Julian, not Gregorian.  In that case more actual historic dates will be correct (8 AD to 1582 AD) than Gregorian (1917..) for a long time.
>   Before 8 AD calendars were a universal mess anyway so I see no competitor for the proleptic Julian calendar.  Unless you want to re-introduce the older and even more regular hellenistic/Egyptian annus vagus, or the Mayan haab, or the Sumerian 360-day administrative count.
>     The Julian calendar may not follow the mean tropical year nor mean spring aequinox year nor sidereal year very accurately, but neither does the Gregorian year, and the latter's intercalation scheme is unnecessarily complex and non-optimal as discussed many times in this list.  So for simplicity and continuity, the Julian calendar is the one of choice over the Gregorian in my opinion.
> --
> Tom Peters
>
>

--
Mark J. Reed <markjreed@...>