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Re: [Cbor] [EXTERNAL] Re: draft-ietf-cbor-date-tag-02 - handling of time zone offsets

Mike Jones <Michael.Jones@microsoft.com> Thu, 16 July 2020 15:58 UTC

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From: Mike Jones <Michael.Jones@microsoft.com>
To: Juergen Schoenwaelder <j.schoenwaelder@jacobs-university.de>, "draft-ietf-cbor-date-tag@ietf.org" <draft-ietf-cbor-date-tag@ietf.org>, "cbor@ietf.org" <cbor@ietf.org>
Thread-Topic: [EXTERNAL] Re: draft-ietf-cbor-date-tag-02 - handling of time zone offsets
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Date: Thu, 16 Jul 2020 15:58:43 +0000
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Subject: Re: [Cbor] [EXTERNAL] Re: draft-ietf-cbor-date-tag-02 - handling of time zone offsets
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Replies inline, prefixed by "Mike>"...

-----Original Message-----
From: Juergen Schoenwaelder <j.schoenwaelder@jacobs-university.de> 
Sent: Thursday, July 16, 2020 6:37 AM
To: draft-ietf-cbor-date-tag@ietf.org; cbor@ietf.org
Subject: [EXTERNAL] Re: draft-ietf-cbor-date-tag-02 - handling of time zone offsets

Thanks for adding new text to -04. I am, however, not sure the text is already resolving all issues.

- I do not understand why you reference IEEE Std 1003.1, 2013 Edition
   [POSIX.1] time epoch 1970-01-01T00:00:00Z UTC if you then say that
   the timezone is irrelevant. If the timezone is irrelevant, you can
   simplify things:

   OLD

   The epoch chosen for the second tag, which represents days since the
   Gregorian calendar date 1970-01-01, is related to the IEEE Std
   1003.1, 2013 Edition [POSIX.1] time epoch 1970-01-01T00:00:00Z UTC
   only insofar as both contain the date 1970-01-01.  This should not be
   construed as indicating that dates using this tag represent either a
   specific time of day and/or time zone.

   NEW

   The epoch chosen for the second tag, which represents days since the
   Gregorian calendar date 1970-01-01.

Mike> Given that many developers know that the UNIX/POSIX Epoch is 1970-01-01T00:00:00Z, others would think it is odd if we *don't* reference it.  I believe the current reference text strikes an appropriate balance, saying how they are and are not related.

- In the section Comparing Dates, I like to see a clear statement that
  dates generated by systems in different timezones for the same event
  may not compare for equality.

Mike> OK

- I do not understand section 1.3. Perhaps you wanted to say that the
  representation of date and time values is already defined in section
  2.4.1 of RFC 7049? (Of course, one could ask the question why you now
  introduce a tag for date values but not at the same time also a tag
  for time values.)

Mike> 1.3 was added in response to comments by Jim Schaad - also with input from Carsten Bormann and is about comparing dates and times.  As to why tags weren't added for time values - there was a present use case for date values and there wasn't for time values.  Another spec can always define and add such tags to the registry in the future.

/js

-- 
Juergen Schoenwaelder           Jacobs University Bremen gGmbH
Phone: +49 421 200 3587         Campus Ring 1 | 28759 Bremen | Germany
Fax:   +49 421 200 3103         <https://www.jacobs-university.de/>

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