How to format dates in a timezone, different to the one the user has configured?

I have a form that should always format the date in a specific timezone, defined in the object record.

I Have tried to override the context 'tz' variable before the view opens, without success.

UPDATE: I saw there is a method: view_init(cr, uid, fields_list, context), but it only works for a new record, there is something like this when I open the view of an existing record?.

UPDATE2: It seems that openerp web ignores the user timezone configured, it just format the date with the browsers timezone, and only shows and alert if they are different, so it is useless to override the context 'tz' variable.