firefox javascript returns wrong data.

tested in Ubuntustudio 11.04 and Xubuntu 11.10

Firefox version 9.0.1 - Mozilla Firefox for Ubuntu canonical - 1.0

On this site:
http://www.permies.com/t/12027/tinkering-site/paul-we-RMH-rocket-stove
(this thread was chosen because I expect little or no more traffic there)

They use a javascript subroutine to show the date at the viewers local time. The input data is the server date/time and the output is supposed to be the local time for the viewer (if they are logged in, but the effect shows logged in or not). Opera, chrome, konqueror show this correctly.

I have included cut and paste from this page for all four browsers of the Message date/times of the first three messages in public mode (me not logged in so that someone with no account will get the same results)

What firefox shows:
------------------------8<---------------------
posted Today 03:53:24 AM
posted Today 07:24:41 AM
posted Today 11:06:51 AM
-------------------------8<--------------------

If the messages had been written last year, it seems that the messages for
one month all appear from the same date... that is messages written in
december show as november 12, messages in november show as november 11. So
it appears that the month ends up being the day and the year as the month.
(fields off by one?)

What chrome shows:
---------------------------8<------------------
posted Monday, January 09, 2012 03:53:24
posted Monday, January 09, 2012 07:24:41
posted Monday, January 09, 2012 11:06:51
---------------------------8<------------------

What opera shows:
-------------------------8<-------------------
posted Monday January 09, 2012 03:53:24
posted Monday January 09, 2012 07:24:41
posted Monday January 09, 2012 11:06:51
------------------------8<--------------------

What Konqueror shows:
---------------------8<-----------------------
posted 12-01-09 03:53:24 AM
posted 12-01-09 07:24:41 AM
posted 12-01-09 11:06:51 AM
--------------------8<------------------------
Different, but still correct... probably a setting difference.

Because I don't know javascript very well, I can't tell if this is the same bug as others though some do look similar. It does mean for me Xubuntu is broken because it's purpose is to be light and yet I will have to install another browser for it to be complete. I am not sure that this is a ubuntu problem, but the version of firefox is ubuntu specific and so I reported it here.