Subject: RE: Duration: Does 1 day == 24 hours?

From: [email-masked]
Date: Wed, 28 Mar 2001 12:22:06 -0600

> Correction: DURATION does not support year and month 
> components.  Week and Day
> are just as precisely defined as Second; both can be defined 
> as a precise
> number of seconds.  See 2445/4.3.6:

Thanks for the correction. We did remove the Y, W and M in the latter stages
of agreement on RFC2445, didn't we. I was looking at ISO 8601 at the same
time and remembered the earlier drafts for iCalendar. My confusion. Thanks.

But that doesn't change the semantics. The DURATION value type allows a mix
of clock and calendar periods. They use different scales.

Yes, you can combine them. Specifying calendar days plus additional clock
periods seemed to be beneficial, albeit more complex.

-- Frank

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From: Alan Davies <[email-masked]>
Date: Wed, 28 Mar 2001 13:52:04 -0500

>periods seemed to be beneficial, albeit more complex.

So what about P1W ? Does that round up to the nearest
Day (assuming it's using the day scale), Week (as it's
using a week scale), or neither?

Btw, where in ISO 8601 http://www.iso.ch/markete/8601.pdf
is it explicitly stated that a calendar period duration
will round up to the nearest day?

One example that seems to contradict your idea is a
representation of a period of time as a Duration and End
(5.5.3.4). As the Time component of the Duration is 12 and
a half hours, and the Time Component of the End is
23:20:50, no rounding off to the nearest day can have
taken place, or this example would be invalid.

--Alan

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From: Patrik Fältström <[email-masked]>
Date: Wed, 28 Mar 2001 22:25:28 +0200

People should read the following document before comparing days and 
hours (or rather, before starting comparing two intervals):

http://www.macchiato.com/unicode/timeIntervals.htm

    paf

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From: John Stracke <[email-masked]>
Date: Wed, 28 Mar 2001 15:02:20 -0500

[email-masked] wrote:

> But that doesn't change the semantics.

But what *are* the semantics? They're not defined in RFC-2445 or in ISO-8601.

> The DURATION value type allows a mix

That cannot be inferred from the text, though.  The only units allowed in 2445
are the ones that are well-defined multiples of one second; to me, the obvious
implication is that any duration can be expressed as some integer number of
seconds.

--
/================================================================\
|John Stracke    | http://www.ecal.com |My opinions are my own.  |
|Chief Scientist |===============================================|
|eCal Corp.      |Diplomacy: The art of letting someone else have|
[email-masked]|your way                                       |
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---

From: "Shannon J. Clark" <[email-masked]>
Date: Wed, 28 Mar 2001 15:21:43 -0600

If this document is currently - or will be in the future - a part of a
standards document, should RFC2445 (and perhaps the related documents as
well) reference this document explicitly?

It appears to give a very detailed and carefully thought out set of rules
and issues revolving around time and duration calculations - it appears very
much as a probably necessary reference work for implementations of
iCalendar - especially if we all want to achieve interoperability.

I.e. if implementations implement basic calculations and measurements of
time differently - we will have interop failures.

Shannon

-----Original Message-----
From: [email-masked]
[mailto:[email-masked]]On Behalf Of Patrik Fältström
Sent: Wednesday, March 28, 2001 2:25 PM
To: [email-masked]
Subject: RE: Duration: Does 1 day == 24 hours?

    paf

---

From: John Stracke <[email-masked]>
Date: Wed, 28 Mar 2001 16:53:44 -0500

"Shannon J. Clark" wrote:

> standards document,

I don't see any reason to expect that it will; it's one person's notes.

--
/==============================================================\
|John Stracke    | http://www.ecal.com |My opinions are my own.|
|Chief Scientist |=============================================|
|eCal Corp.      |A mime is a wonderful thing to waste.        |
[email-masked]|                                             |
\==============================================================/