Subject: Re: [IPTEL] CPL: Timezone issues

From: [email-masked]
Date: Mon, 10 Jul 2000 14:41:07 -0400

From:  Tom Gray@MITEL on 07/10/2000 02:41 PM

This may seem like an obvious question but my reading of the draft doesn't
answer it.

What happens if there are two 1:30 am's on a single day or none? These are the
cases in which the time reverts to 1am from 2am and when the time jumps fromm
1am to 2pm which are typical of day light saving handling. How will a script
specifying 1:30 am cope with these situations? How will defined time ranges be
affected?

Jonathan Lennox <[email-masked]> on 07/10/2000 02:25:42 PM

To:   Rohan Mahy <[email-masked]>
cc:   [email-masked] (bcc: Tom Gray/Kan/Mitel)

Subject:  Re: [IPTEL] CPL: Timezone issues

On Mon, July 10 2000, "Rohan Mahy" wrote to "Jonathan Lennox,
[email-masked]" saying:

> I guess the question is, do SIP user agents and proxies executing CPL
> scripts really care about the timezone *name*?
>
> If each proxy or user agent simply knows their own current UTC-offset, is
> this good enough?

They don't care about timezone names.  They do, however, care about a
timezone's daylight-savings transition rules, because a script to do
something between 9 am and 5 pm shouldn't suddenly become a script to do
something between 8 am and 4 pm in late autumn.

Unfortunately, there are hundreds of different DST transition rules around
the world, and politicians muck with them on a regular basis.  This is the
problem we're trying to solve here, or alternately defer to someone else.

--
Jonathan Lennox
[email-masked]

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From: Jonathan Lennox <[email-masked]>
Date: Mon, 10 Jul 2000 15:25:38 -0400 (EDT)

> specifying 1:30 am cope with these situations? How will defined time ranges be

Since the CPL only specifies time ranges, not actual events, I think this is
only a problem for the fall-back case (repeated times), not the
spring-forward case (skipped times).  I think start times should be assumed
to be the earlier instance of the time, while end times should be the latter
instance.  I'll add a sentence about this.

-- 
Jonathan Lennox
[email-masked]