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

From: [email-masked]
Date: Wed, 28 Mar 2001 15:39:43 -0600

> No, it's an event which lasts from say 1700 one day to 1700 the next. 
> Just like one month after jan 2 is feb 2, and one month after feb 2 
> is march 2.
> 
> You can not convert from one unit to another.

Not sure. 

One on point, I believe that the end specifies when the meeting ends. That
is, it is not inclusive in the event. So, in your example, it would end at
T165959. 

On a second point, I believe that to say that the DURATION is P1D means that
the event lasts one day. The day, according to ISO8601, ends at T240000 that
night. The month ends at T240000 on the last night of the month. The year
ends at T2400000 on the last day of the year. 

So, I would think that specifying a DURATION in days gives you a granularity
based on the calendar, not on the clock. If you say the meeting is for
January 2nd and has a duration of one day, then it ends at T240000 that
night.

-- Frank

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From: Patrik Fältström <[email-masked]>
Date: Thu, 29 Mar 2001 07:16:59 +0200

>January 2nd and has a duration of one day, then it ends at T240000 that

I was thinking of the case when you have a starting time which is not 
zero modulo the length of the duration, i.e. that you have a start at 
1700 a certain day, and then a duration of one day.

Better example might be start at 1700 a tuesday and duration of a 
week, or even start at 1700 on the 2nd of february and duration of a 
month.

This _is_ hard, but I don't see that implementations _have_ to 
implement these kind of things.

If we have a change to DST (which means that we move the clock one 
hour forward at 0200), and an event which starts at 0130, with 
duration of 1 hour should of course stop at 0330. 0230 doesn't exist 
that day. Does the other alternative mean that the event doesn't have 
any end at all?

   paf

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From: Alan Davies <[email-masked]>
Date: Thu, 29 Mar 2001 11:18:37 -0500

At 07:16 2001-03-29 +0200, [email-masked]:
>Better example might be start at 1700 a tuesday and duration of a week

Now that you mention week durations again, does anyone else agree with
the Frank Dawson's interpretation that when using "calendar scale"
durations (day and week) with a date-time DTSTART, one should use the
"date-time to determine the calendar scale and then apply the duration to
that."?

The impact of this would be that an event starting at 17:00 on
Tuesday with a P1W duration, would end at 24:00 on Sunday
(Sunday night being the end of an ISO standard work week).
An event starting sometime on Saturday with a P1W duration would
also finish at 24:00 on Sunday. I have no idea when an event with
a duration like P1W1DT1H would end- your guess is as good as mine.

--Alan