[LEAPSECS] Definition of Standard time - Brooks Harris

[Brooks Harris]

On 2014-02-16 01:28 AM, John Hawkinson wrote:

> This is not a real conflict.

>

> The standards you cite do not say "standard time,"

> they say things like "standard time scale" which is parsed as

> (STANDARD (TIME SCALE)) not ((STANDARD TIME) SCALE).

> etc.

Ah, they are defining "standard time", "standard time of day", and 
"clock time".

The note on ISO 8601, 2.1.14 "standard time" says "NOTE This time shift 
may be varied in the course of a year."

The note on IEC 60050-111, 111-16-16 "standard time" (that ISO 8601 
references) says "NOTE Examples are Central European Time (CET), Central 
European Summer Time (CEST), Pacific Standard Time (PST), Japanese 
Standard Time (JST), etc."

That includes *both* CET and CEST.

The note on ISO 8601, 2.1.15 "standard time of day" says "NOTE Standard 
time of day is called "clock time" in IEC 60050-111."

And IEC 60050-111, 111-16-17 "clock time" describes time as indicated 
for "local standard time"

It seems pretty clear they mean "standard time" may include "summer 
time". That really *is* in conflict with common use, isn't it?

This comes up in context of attempting to write a definition of 
"standard time" as understood in common use (and POSIX, and such). You'd 
like to reach to ISO 8601 for the definition, and there you discover 
this conflict.

ISO 8601 is an important standard. Besides its famous description of 
"representation" is also defines what its representing (Basic concepts, 
Time Units, Gregorian calendar).

But it is silent on "daylight savings". It describes representation of 
"Local time and the difference from UTC", and "local time" is defined in 
2.1.16 - local time - locally applicable time of day such as standard 
time of day, or a non-UTC based time of day

It can't, or doesn't, distinguish between New York "standard time" 
12:00:00-05:00 and New York "daylight time" 12:00:00-04:00.

"Standard time" in 8601 really is in conflict with common use, I think.

-Brooks

>

> Not optimal but so little in life is.

>

> --jhawk at mit.edu

>    John Hawkinson

>    +1 617 797 0250

>

> Brooks Harris <brooks at edlmax.com> wrote on Sun, 16 Feb 2014

> at 01:23:23 -0800 in <5300838B.8030503 at edlmax.com>:

>

>

>> Date: Sun, 16 Feb 2014 01:23:23 -0800

>> From: Brooks Harris <brooks at edlmax.com>

>> To: Leap Second Discussion List <leapsecs at leapsecond.com>

>> Subject: [LEAPSECS] Definition of Standard time - Brooks Harris

>> X-Virus-Check-By: mailwash27.pair.com

>> X-TCPREMOTEIP: 76.176.132.16

>> X-Authenticated-UID: brooks at edlmax.com

>> Message-ID: <5300838B.8030503 at edlmax.com>

>> Reply-To: Leap Second Discussion List <leapsecs at leapsecond.com>

>> Sender: leapsecs-bounces at leapsecond.com

>>

>> It seems the meaning of the term "Standard time" in common-use and

>> in POSIX is in conflict with the definitions in ISO 8601 and IEC

>> 60050-111.

>>

>> Wikipedia (not always an authoritative source)

>> Standard time

>> http://en.wikipedia.org/wiki/Standard_time

>> states:

>>

>> "Where daylight saving time is used, the term standard time

>> typically refers to the time without the offset for daylight saving

>> time.".

>>

>> That is consistent with my understanding of "Standard time".

>>

>> POSIX doesn't seem to explicitly state this, but the logic of the TZ

>> environment and functions are consistent with this definition.

>>

>> But ISO 8601 and IEC 60050-111 say "standard time" may include time

>> shifts for "winter time" and "summer time":

>>

>> In ISO 8601 ----------------

>>

>> 2.1.14

>> standard time

>> time scale derived from coordinated universal time, UTC, by a time

>> shift established in a given location by the

>> competent authority

>> [IEC 60050-111]

>> NOTE This time shift may be varied in the course of a year.

>>

>> 2.1.15

>> standard time of day

>> quantitative expression marking an instant within a calendar day by

>> the duration elapsed after midnight in the

>> local standard time

>> [IEC 60050-111]

>> NOTE Standard time of day is called ?clock time? in IEC 60050-111.

>>

>> In IEC 60050-111 ---------------

>>

>> 111-16-16

>> standard time

>> time scale derived from coordinated universal time, UTC, by a time

>> shift established in a

>> given location by the competent authority

>> NOTE Examples are Central European Time (CET), Central European

>> Summer Time (CEST), Pacific

>> Standard Time (PST), Japanese Standard Time (JST), etc.

>>

>> 111-16-17

>> clock time

>> quantitative expression marking an instant within a calendar day by

>> the duration elapsed after

>> midnight in the local standard time

>> NOTE Usually, clock time is represented by the number of hours

>> elapsed after midnight, the number

>> of minutes elapsed after the last full hour, and, if necessary, the

>> number of seconds elapsed after the

>> last full minute, possibly with decimal parts of a second. Examples

>> of the standardized representation

>> (see ISO 8601) are 09:01; 09:01:12; 09:01:12,23.

>>

>> -----------

>>

>> Is my interpretation correct? Can anyone shed light on how and why

>> ISO 8601 and IEC 60050-111 are in conflict with common use and POSIX

>> and how this may have come about?

>>

>> -Brooks

>>

>>

>>

>>

>> _______________________________________________

>> LEAPSECS mailing list

>> LEAPSECS at leapsecond.com

>> http://six.pairlist.net/mailman/listinfo/leapsecs

>


-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://six.pairlist.net/pipermail/leapsecs/attachments/20140216/05175c79/attachment.html>