Rails 3: setting the timezone to the current users timezone

I put this in Application Controller:

before_filter :set_timezone 

def set_timezone  
Time.zone = current_user.time_zone 
end  

But I always get the error:

undefined m开发者_如何转开发ethod time_zone for #<User:0xa46e358>

and I just don't know why...

I hope someone can help

Further to Jesse's answer, I should add that you can generally avoid adding a new column in db and just create a custom method in user model and make use of cookie to get the user's timezone:

in client-side (js):

function set_time_zone_offset() {
    var current_time = new Date();
    $.cookie('time_zone', current_time.getTimezoneOffset());
}

in Application Controller:

before_filter :set_timezone 

def set_timezone  
 min = request.cookies["time_zone"].to_i
 Time.zone = ActiveSupport::TimeZone[-min.minutes]
end 

Max -- the ryandaigle.com article you mentioned links to this writeup where you need to create a migration to add "time_zone" as an attribute to the user

(this is from the article, in rails 2.x syntax)

$ script/generate scaffold User name:string time_zone:string
$ rake db:migrate

later

<%= f.time_zone_select :time_zone, TimeZone.us_zones %>

That's why your .time_zone is returning a method_missing -- you haven't stored the time_zone on the user yet.

function set_time_zone_offset() {
  var current_time = new Date();
  $.cookie('time_zone', current_time.getTimezoneOffset());
}

This is not correct, because time offset is not constant, it depends on daylight saving time periods. Rails expects the standard time offset when calling ActiveSupport::TimeZone[-min.minutes].

ex: in France at date 09/03/2013 10:50:12 +02:00, your javascript will return -120 as offset where ActiveSupport will need -60 to resolve France timezone.

Then you need to check if this is a daylight saving time period in JS then if this is the case you will have to substract one hour to the offset to get the right value used by Rails.