Rails: get #beginning_of_day in time zone

Question

I have a default time zone setup for the rails application. And an instance of the Date object.

How can I get make Date#beginning_of_day to return the beginning of the day in the specified time zone, but not my local timezone.

Is there any other method to get beginning of the day time in the specified timezone for the given date?

date = Date.new(2014,10,29)

zone = ActiveSupport::TimeZone.new('CET')
date.foo(zone) # should return "Wed, 29 Oct 2014 00:00:00 CET +01:00"

zone = ActiveSupport::TimeZone.new('UTC')
date.foo(zone) # should return "Wed, 29 Oct 2014 00:00:00 UTC +00:00"

Answer 1

ActiveSupport::TimeZone['Europe/London'].parse('30.07.2013') # 2013-07-29 23:00:00 UTC 
ActiveSupport::TimeZone['Asia/Magadan'].parse('30.07.2013') # 2013-07-29 12:00:00 UTC

Answer 2

As Leonid Shevtsov mentioned, Date.beginning_of_day does not honor Time.zone in ActiveSupport 2.3

An alternative I used, if your stuck using Rails 4.0 or ActiveSupport 2.3, and you need to use a custom date:

date = Date.new(2014,10,29)
date.to_time.change(hour: 0, min: 0, sec: 0).in_time_zone  #.beginning_of_day
date.to_time.change(hour: 23, min: 59, sec: 59).in_time_zone #.end_of_day

Results:

2.0.0-p247 :001 > date = Date.new(2014,10,29)
 => Wed, 29 Oct 2014 

2.0.0-p247 :002 > date.to_time.change(hour: 0, min: 0, sec: 0)
 => 2014-10-29 00:00:00 -0500 

2.0.0-p247 :003 > date.to_time.change(hour: 0, min: 0, sec: 0).in_time_zone
 => Wed, 29 Oct 2014 05:00:00 UTC +00:00 

2.0.0-p247 :004 > date.to_time.change(hour: 23, min: 59, sec: 59)
 => 2014-10-29 23:59:59 -0500 

2.0.0-p247 :005 > date.to_time.change(hour: 23, min: 59, sec: 59).in_time_zone
 => Thu, 30 Oct 2014 04:59:59 UTC +00:00 

My original failed model scope using .beginning_of_day to .end_of_day failed to work:

scope :on_day, ->(date) { where( created_at: date.beginning_of_day..date.end_of_day ) }

And, this is what fixed it, since I could not upgrade to Rails 4.0

scope :on_day, ->(date) { where( created_at: date.to_time.change(hour: 0, min: 0, sec: 0).in_time_zone..date.to_time.change(hour: 23, min: 59, sec: 59).in_time_zone ) }