[Ietf-calsify] Section 4.2.19 Time Zone Identifier: TZID parameter specified on DATE property

[Clint Talbert]

Bernard Desruisseaux wrote:
> Section 4.2.19 Time Zone Identifier of RFC 2445 says nothing about the
> use of the TZID parameter on DATE properties. This section specifies
> when this parameter MUST or MUST NOT be specified on DATE-TIME or TIME
> values, but says nothing about DATE.
>
> Furthermore, unlike section 4.3.5 Date-Time, section 4.3.4 Date doesn't
> discuss the TZID parameter at all.
>
I'm glad that you're addressing this because I believe the behavior you 
note resulted from a misunderstanding of section 4.3.4.
> .. snip..

> To find out whether Mozilla Sunbird actually cares about the TZID
> itself I changed my time zone to America/Montreal (UTC-4:00). Given
> that June 28th, 2007 00:00 (midnight) Asia/Shanghai corresponds to
> June 27th, 12:00 (noon) America/Montreal I was wondering if this
> All Day event would be displayed on June 27th, 2007. It turns out
> that Mozilla Sunbird still displayed the event on June 28th.
>
I believe this is the proper behavior, to tie the all-day event to a 
specific numerical date.  It sounds like you also think so, given the 
change you suggest below.
>    Note: If you want to try this yourself with Mozilla Sunbird,
>    you'll actually need to change the time zone of your OS to
>    match the time zone you configured in Mozilla Sunbird.  Else
>    Mozilla Sunbird will end up creating the All Day event on the
>    wrong day altogether. For instance, if you configure Sunbird
>    with Asia/Shanghai but have your OS configured with
>    America/Montreal and create an All Day event on June 28th, 2007,
>    Mozilla Sunbird will create an All Day event that start on
>    June 29th!
>
This is an unfortunate, known issue in Sunbird/Lightning that we are 
addressing in our next (0.7) release (work is actually underway on it, 
though the bug report below does not reflect it). I apologize for the 
inconvenience. 

For more information, please see: 
https://bugzilla.mozilla.org/show_bug.cgi?id=337191.  And if you'd like 
to be notified of changes to the bug, feel free to CC yourself on it.
>
> I propose to change the following statement in section 4.2.19 Time Zone
> Identifier, from:
>
> > The TZID property parameter MUST NOT be applied to DATE-TIME or TIME
> > properties whose time values are specified in UTC.
>
> to:
>
> > The TZID property parameter MUST NOT be applied to DATE properties,
> > and DATE-TIME or TIME properties whose time values are specified in
> > UTC.
>
Hooray!  I second the change.

I'll file another bug to no longer add TZID to DATE properties in 
Sunbird as well.  Thanks for bringing this to our attention. :-)

Thanks,

Clint Talbert
Mozilla Calendar Project QA Coordinator