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RE: ACTION-129: Expressing timezones in the Calendar API

From: <richard.tibbett@orange-ftgroup.com>
Date: Fri, 26 Mar 2010 18:25:44 +0100
Message-ID: <19791_1269624354_4BACEE22_19791_14645_1_355A518BC0575547B2A3D6773AAF8EEFA82C72@ftrdmel1>
To: <andrew@morphoss.com>
Cc: <pgladstone@cisco.com>, <public-device-apis@w3.org>
On Thurs, 25 Mar 2010 at 20:39, Andrew McMillan wrote:
> 
> On Thu, 2010-03-25 at 12:46 +0100, richard.tibbett@orange-ftgroup.com
> wrote:
> > 
> > What we need is date and time information without any timezone 
> > implications associated with it - so we can apply any 
> timezone value 
> > to any simple date/time object.
> > 
> > So I see 4 options:
> > 
> > 1. define a custom W3C 'Date' interface with no timezoned info (or 
> > Olson Timezone Identifiers only in this W3C Date interface).
> > 2. define a way remove (or set) the timezone on an ECMA Date object.
> > 3. include wording in the spec to say that all timezone information 
> > derived on an ECMA Date in a TimezonedDate object must be ignored. 
> > (this is probably only going to confuse developers further and is 
> > likely not worth considering) 4. revert to the existing 
> format used in 
> > the Calendar API spec for 'Date' objects e.g. 2010-03-25T11:24:19 - 
> > thereby removing dependence on the ECMA Date interface.
> > 
> > Any preferences on the above options? I would suggest option 1 is 
> > where we want to go (though we're getting in to ECMA standards 
> > territory and I'd personally prefer them to take up option 
> 2 if possible).
> 
> It does sound rather like a rock and a hard place, and it's 
> unfortunate that the ECMA standard does not already have 
> fully functional timezone information.
> 
> I think it's worth at least raising the issue with the ECMA 
> folk so that they can start whatever process is needed to 
> remedy their problems.

I agree, though I don't have any formal liason with ECMA. Can another
member of our group (or the group itself) ask for feedback on option 2
from ECMA??

> 
> Beyond that, though, I would agree that (1) is very likely 
> the best option.
> 

I've been thinking about this considerably today...perhaps I should
mention that I think I've looked at this from pretty much every angle
out there over the last few hours.

Sometimes the simplest solutions are the hardest to see but after a lot
of iterations (and a great deal of Javascript coding) I re-factored a
new proposal to the following:

WebIDL:
-------

[NoInterfaceObject]
interface TimezonedDate {
    attribute int year;
    attribute int month;
    attribute int day;
    attribute int? hours;
    attribute int? minutes;
    attribute int? seconds;

    attribute DOMString? tz;
};


Usage:
------

// Floating TimezonedDate Object:
{
	day: 26,
	month: 3,
	year: 2010,
	hours: 16,
	minutes: 58,
	// missing 'seconds' default to zero
	// missing or null 'tz' indicates that this object is not
timezone-bound
}

// Timezone-bound TimezonedDate Object:
{
	day: 26,
	month: 3,
	year: 2010,
	hours: 16,
	// missing 'minutes' default to zero
	seconds: 30,
	tz: 'America/New_York'
}


This object satisfies the three original requirements in [1].

The proposal here is to only store and communicate the properties that
are required to reconstruct a date and time object on any given platform
without getting in to the gritty details of timezone reconstruction
ourselves in the spec. We also side-step the issues with the ECMA Date
object (though the parameters provided can be used by a developer to
construct an ECMA Date object if desired). 

So what do we think...can we live with this?

- Richard


[1]
http://lists.w3.org/Archives/Public/public-device-apis/2010Mar/0203.html


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Received on Friday, 26 March 2010 17:26:27 GMT

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