Bug#518486: iceweasel: Iceweasel handles dates in Javascript incorrectly

[Mike Hommey]

On Sun, Dec 20, 2009 at 10:36:58PM +0000, Alan Chandler wrote:
> Mike Hommey wrote:
> >On Sun, Dec 20, 2009 at 09:55:35AM +0000, Alan Chandler wrote:
> >>Mike Hommey wrote:
> >>>On Sat, Dec 19, 2009 at 11:55:57PM +0000, Alan Chandler wrote:
> >>>>BUT I AN NOT IN GMT+1 at that point.  I am at GMT. So it SHOULD
> >>>>return 0, as do all the other browsers I mention
> >>>What does d.getTimezoneOffset() return ?
> >>>
> >>>Mike
> >>On Iceweasel and Konqueror  TimezoneOffset gives -60
> >>
> >>On Epiphany under Linux and With IE, Chrome, Safari and Safari
> >>running in XP in a Virtual Box on the same machine I get
> >>TimezoneOffset = 0
> >
> >What happens when you set your system date to some time in summer
> >time ?
> >
> >Mike
> 
> I am not sure I did it right, changed with date --set="..." to
> sometime in June but I got exactly the same answers.

In the meantime, I got the real issue: you are assuming the time offset
is GMT, while it is NOT.

When doing Date(0), what you are doing is getting the date at 0 seconds
after the first of january, 1970, midnight. Guess what time offset was
used at that date ? You would assume GMT, right ? Wrong:

   RoSPA suggest this would reduce the number of accidents over this
   period as a result of the lighter evenings, as was demonstrated when
   the British Standard Time scheme was trialled between 27 October 1968
   and 31 October 1971, when Britain remained on GMT+1 all year.

Yes, 1 January 1970 0:0:0 was GMT+1.

This means Iceweasel and Konqueror are right. And all the others are
wrong.

$ TZ=Europe/London date -d '1/1/1970 0:0:0'
Thu Jan  1 00:00:00 BST 1970

$ TZ=Europe/London date -d '1/1/1970 0:0:0' +%z
+0100

Mike