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Bug 13152 - How can DST be derived from time zone offset -04:00?
Summary: How can DST be derived from time zone offset -04:00?
Status: RESOLVED NEEDSINFO
Alias: None
Product: HTML WG
Classification: Unclassified
Component: LC1 HTML5 spec (show other bugs)
Version: unspecified
Hardware: Other other
: P3 minor
Target Milestone: ---
Assignee: Ian 'Hixie' Hickson
QA Contact: HTML WG Bugzilla archive list
URL: http://www.whatwg.org/specs/web-apps/...
Whiteboard:
Keywords:
Depends on:
Blocks:
 
Reported: 2011-07-05 19:59 UTC by contributor
Modified: 2011-08-04 05:34 UTC (History)
6 users (show)

See Also:


Attachments

Description contributor 2011-07-05 19:59:50 UTC
Specification: http://www.whatwg.org/specs/web-apps/current-work/multipage/common-microsyntaxes.html
Multipage: http://www.whatwg.org/C#global-dates-and-times
Complete: http://www.whatwg.org/c#global-dates-and-times

Comment:
How can DST be derive d from time zone offset -04:00?

Posted from: 93.216.203.46
User agent: Mozilla/5.0 (Windows NT 6.1; rv:5.0) Gecko/20100101 Firefox/5.0
Comment 1 Philip Jägenstedt 2011-07-06 08:26:12 UTC
It can't, DST is part of the offset. To know if DST applies, you have to know which country the timestamp is from, as DST varies depending on what lawmakers pull out of their hats.
Comment 2 Aryeh Gregor 2011-07-06 20:06:46 UTC
This does not appear to contain any feedback on the specification.  Marking INVALID.  For information about daylight saving time, the Wikipedia article is probably a good place to look:

http://en.wikipedia.org/wiki/Daylight_saving_time
Comment 3 Alexander Veit 2011-07-06 20:14:01 UTC
To cite the current spec:

"1979-10-14T12:00:00.001-04:00
One millisecond after noon on October 14th 1979, in the time zone in use on the east coast of the USA during daylight saving time."

This is confusing, since the time zone cannot be derived from the offset. Offset to time zone is a 1:n correspondence.
Comment 4 Aryeh Gregor 2011-07-06 21:39:44 UTC
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Status: Additional Information Needed
Change Description: no spec change
Rationale: What exactly is incorrect with the spec text you cite?  UTC-04:00 is in fact the time zone in use on the east coast of the USA during daylight saving time.  It is also the time zone in use in a number of other places, such as parts of Latin America and the Caribbean, but that doesn't make the example incorrect.
Comment 5 Alexander Veit 2011-07-07 21:13:09 UTC
(In reply to comment #4)
> Rationale: What exactly is incorrect with the spec text you cite?  UTC-04:00 is
> in fact the time zone in use on the east coast of the USA during daylight
> saving time.  It is also the time zone in use in a number of other places, such
> as parts of Latin America and the Caribbean, but that doesn't make the example
> incorrect.

OK. My first reading of the example was that the time zone (... in use on the east coast of the USA during daylight saving time) would be implied by the given date-time literal, what is certainly not correct.

But as far as I can see, the only time zone that is relevant for this spec is UTC, what perfectly corresponds with the lack of calendaring support in ECMAScript. So the example may probably not confuse readers too much.

Sorry for the noise.
Comment 6 Michael[tm] Smith 2011-08-04 05:34:59 UTC
mass-move component to LC1