timestamp notation @gnupg.org

Jerome Baum jerome at jeromebaum.com
Sat Jun 18 23:50:08 CEST 2011

>> I don't have ISO 8601 handy, so I can't speak
>> first hand. However, this example seems very rational:
>> "The 20th Century 1901-01-01 / P100Y
>> 1901-01-01 T 00:00:00 / 2001-01-01 T 00:00:00"
> I would prefer to say the century finished at 2000-12-31T24:00:00. (-;
> Also, I think 1901-01-01T00:00:00/2001-01-01T00:00:00
> would be equivalent to 1901-01-01T00:00:00/P100Y,
> and 1901-01-01/2001-01-01 would be equivalent to 1901-01-01/P100Y.
> They are different in the same way as 5 Euros is different to
> 5.00 Euros.

Exactly. 5 Euros is still 5 Euros, whether you say "5,00 Euros", "5,--
Euros", "5 Euros, but no cents", "5 Euros exactly", "5 Euros sharp",
or just "5 Euros". Still the same thing.

>> Ah, we've been careless. Append a "Z" to your dates and
>> they are UTC (or append a timezone, if you want that).
>> Those two intervals are actually ambiguous AFAIK. We
>> could specify either:
>> 1. All times must be UTC ("Z") or have a timezone; or
> Aren't the timestamps recorded in the signature packets as unix time
> [1], and displayed in the local time detected from the user's system?

I was referring to the interval notation.

>> 2. Ambiguous times are interpreted as UTC.
> I think the ISO 8601 standard assumes local time unless otherwise
> specified. So it makes sense for each person viewing the signature to
> see the timestamp in their own local time if no time zone information
> is included.

Except, what is "local time" if you have two people in different
timezones? That's why we'd need either the "all times UTC" rule, or a
forced timezone in the field.

> 20110618T000000+0200/P1D and 20110617T230000+0100/P1D both refer to
> the same time period without ambiguity.

Those have timezones. Your (and my) previous examples didn't.

> If people feel there is ambiguity here, maybe this is best dealt with
> by adding some simple text to the GnuPG output to indicate that times
> are shown in local time, as per the user's system.

That isn't what I was referring to. 20110618T000000/P1D is ambiguous:
Is it 20110618T000000+0200/P1D or 20110618T000000+0100/P1D ?

Jerome Baum
tel +49-1578-8434336
email jerome at jeromebaum.com
web www.jeromebaum.com
PGP: A0E4 B2D4 94E6 20EE 85BA E45B 63E4 2BD8 C58C 753A
PGP: 2C23 EBFF DF1A 840D 2351 F5F5 F25B A03F 2152 36DA

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