Issue comparing DateTime/Time in different zones in Rails - ruby-on-rails

Question

In my application the user sets a specific end time for a task. When a task is loaded, it creates a corresponding CheckIn using that task's information (self in this case is the task):
def create_checkin_end_time(day)
week = (Date.today .. Date.today + 6)
week.each do |day_of_week|
if day_of_week.strftime("%A") == day
return DateTime.new(day_of_week.year, day_of_week.month, day_of_week.day, self.end_time.hour, self.end_time.min)
end
end
end
I've set config.time_zone equal to "Eastern Time (US & Canada") but instead of creating the task as UTC it submits as EST then subtracts 4 hours from that.
[2] pry(main)> CheckIn.last.end_time
CheckIn Load (0.7ms) SELECT "check_ins".* FROM "check_ins" ORDER BY "check_ins"."id" DESC LIMIT 1
=> Sun, 20 Oct 2013 19:30:00 EDT -04:00
[3] pry(main)> Task.last.end_time
Task Load (0.7ms) SELECT "tasks".* FROM "tasks" ORDER BY "tasks"."id" DESC LIMIT 1
=> Sun, 20 Oct 2013 23:30:00 EDT -04:00
The end time for that instance of the model should be 11 PM, based on the task that was used to create it. This is my first go at working with time in Rails so any help would be really appreciated. Thank you.
UPDATE:
Switched it back to UTC and added the method to ApplicationController, but the real problem here was the way I was creating the CheckIn. Because Task.end_time was used as reference in the creation and was called out of the database as EST, the offset was doubled in the creation of the CheckIn. Real weird. My solution was to use .change on creation:
CheckIn.create(task_id: self.id, start_time: self.create_checkin_start_time(day).change(:hour => self.start_time.hour + 4), end_time: self.create_checkin_end_time(day).change(:hour => self.end_time.hour + 4))
This is by NO MEANS a great/permanent solution. I'm in a bit of a time-crunch at the moment and this will suit my needs.

Answer 1

I'd recommend leaving config.time_zone as UTC so you don't see these kind of weird changes happening in the database.
If you want to force a particular timezone on the users of the application, then your best bet is as a before_filter inside ApplicationController:
before_filter :set_timezone
def set_timezone
Time.zone = "Eastern Time (US & Canada)"
end
That way then, all the times will be saved to the database as UTC times, but will be displayed on the site as being in Eastern time.
The reasons for doing this are pretty simple: it's easier to convert from one universal central time (UTC) than it is to convert from some arbitrary point back to UTC and then to some other arbitrary point.