gistfile1.rb

# admin/dealers_controller.rb

class Admin::DealersController < Admin::BaseController
  def new
    @dealer = Dealer.new
    7.times do |i|
      @dealer.hours.build(day: i)
    end
end

# dealer.rb
#
# Schema looks like
# id, dealer_id, day (int mapped to day of week. sun - 0 to sat - 6), open (time column), close (time column),
# created_at, updated_at

class Dealer < ActiveRecord::Base
  has_many :hours
  accepts_nested_attributes_for :hours
end

# dealers/new.html.haml

= form_for [:admin, @dealer], html: { class: 'form-horizontal' } do |f|
  ...
  ...
  %fieldset
    %legend Hours of Operation
    = f.fields_for :hours do |h|
      .control-group
        = h.label :monday, class: 'control-label'
        .controls
          .input-append
            = h.text_field :open, class: 'span1'
            %span.add-on am
            &mdash;
            = h.text_field :close, class: 'span1'
            %span.add-on pm