Re: Draft profile of ISO 8601

Misha Wolf (misha.wolf@reuters.com)
Tue, 24 Jun 1997 18:48:26 +0000 (GMT)


Date: Tue, 24 Jun 1997 18:48:26 +0000 (GMT)
From: Misha Wolf <misha.wolf@reuters.com>
Subject: Re: Draft profile of ISO 8601
In-Reply-To: 
To: Time Zones <tz@elsie.nci.nih.gov>, meta2 <meta2@mrrl.lut.ac.uk>,
        www-html <www-html@w3.org>
Message-Id: <5826481824061997/A79312/REDMS1/11B6C4B01A00*@MHS>

Dan Connolly wrote:
>
> Misha Wolf wrote:
> 
> > 2.  Date plus hours and minutes
> > -------------------------------
> > 
> > The format is one of: YYYY-MM-DDThh:mmZ
> >                       YYYY-MM-DDThh:mm+hh:mm
> >                       YYYY-MM-DDThh:mm-hh:mm
> 
> A major benefit of using YYYY-MM-DD over the Internet
> traditional Tue, 30 Jan 1997... format is that string
> comparisons work for date comparisons; e.g. you don't
> have to go through heroics to sort log files by date.
> 
> By including timezone stuff (+hh:mm), you lose that
> benefit.
> 
> Is there some motivation for including +yy:mm that
> offsets this loss?

[Note: For "+yy:mm" read "+hh:mm"]

I'm not sure which of the following you are asking:

Q1. Why have time zone info?

Q2. Why not require that all dates/times be normalised to UTC when entered.

Answer to Q1: A time is only meaningful within a time zone.

Answers to Q2:

a)  I'm defining a profile with various options (this can be viewed as 
    a family of profiles), such that each adopting standard can choose 
    the appropriate options.  For many purposes, the actual time zone 
    is important.  PICS, for instance, requires the time zone.

b)  The normalisation to UTC can easily be done prior to date/time 
    collation/comparison.  It involves just an addition or subtraction.

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