How do I change the zone offset for a time in Ruby on Rails?

Question

I have a variable foo that contains a time, lets say 4pm today, but the zone offset is wrong, i.e. it is in the wrong time zone. How do I change the time zone?

When

Answer 1

Option 1

Use date_time_attribute gem:

my_date_time = DateTimeAttribute::Container.new(Time.zone.now)
my_date_time.date_time           # => 2001-02-03 22:00:00 KRAT +0700
my_date_time.time_zone = 'Moscow'
my_date_time.date_time           # => 2001-02-03 22:00:00 MSK +0400

Option 2

If time is used as an attribute, you can use the same date_time_attribute gem:

class Task
  include DateTimeAttribute
  date_time_attribute :due_at
end

task = Task.new
task.due_at_time_zone = 'Moscow'
task.due_at                      # => Mon, 03 Feb 2013 22:00:00 MSK +04:00
task.due_at_time_zone = 'London'
task.due_at                      # => Mon, 03 Feb 2013 22:00:00 GMT +00:00