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

Juergen Schoenwaelder <j.schoenwaelder@jacobs-university.de> Fri, 03 July 2020 06:46 UTC

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Date: Fri, 03 Jul 2020 08:46:52 +0200
From: Juergen Schoenwaelder <j.schoenwaelder@jacobs-university.de>
To: Carsten Bormann <cabo@tzi.org>
Cc: draft-ietf-cbor-date-tag@ietf.org, Michael Richardson <mcr+ietf@sandelman.ca>, cbor@ietf.org
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Subject: Re: [Cbor] draft-ietf-cbor-date-tag-02 - handling of time zone offsets
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On Fri, Jul 03, 2020 at 08:29:01AM +0200, Carsten Bormann wrote:
> 
> 
> > (3) a 'date' value and a 'number of days since 1970-01-01' value can
> >     be "inconsistent".
> 
> Not sure how that can be; a common Gregorian calendar seems to be in use.
>

A system may have determined a local date 1970-01-01, which in UTC is
1969-12-31 or 1970-01-01 or 1970-01-02. Hence, days since 1970-01-01
may be -1, 0, or 1, depending on how this is calculated. If the
'number of days since 1970-01-01' is always calculated in the same
unknown local timezone as the local date value, the problem goes away,
but it is likely difficult to enforce this (unless timzone information
is explicit).

/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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