title: Change method on a Time class is not working Rails
body: <p>So I have this an event that i use with fullcalendar-rails. I dont want to use a datetime format because it automatically creates a date selector for both variable(and fullcalendar needs to receive date/time). I would rather have a date selector and 2 time selectors. So i tried doing that but the time_selector will automatically generate a default date. </p>
  
  <p>So I look at the class Time docs and I found that there is a method called change <a href="http://apidock.com/rails/Time/change" rel="nofollow">http://apidock.com/rails/Time/change</a>. So, every thing works but it just wont modify the default date of the time selector to the date of the date selector?? But when I try it in my console it works perfectly..? Very confuse any help would be greatly appreciated Thank.</p>
  
  <p><strong>Events controller</strong> </p>
  
  <pre><code>def create  
      @user = User.find(current_user)
      @event = @user.events.new(event_params)
      @event.user_id = @user.id
      @event.save
      respond_with(@event)
    end
  </code></pre>
  
  <p><strong>Event.rb</strong></p>
  
  <pre><code>before_save :date_setter
  
    def date_setter
      data = self.date
      self.start = self.start.change(:year =&gt; data.year, :month =&gt; data.month, :day =&gt; data.day)
    end
  </code></pre>
  
  <p><strong>_form.html.erb</strong></p>
  
  <pre><code>&lt;%= form_for(@event, url: :user_events) do |f| %&gt;
    &lt;% if @event.errors.any? %&gt;
      &lt;div id="error_explanation"&gt;
        &lt;h2&gt;&lt;%= pluralize(@event.errors.count, "error") %&gt; prohibited this event from being saved:&lt;/h2&gt;
  
        &lt;ul&gt;
        &lt;% @event.errors.full_messages.each do |message| %&gt;
          &lt;li&gt;&lt;%= message %&gt;&lt;/li&gt;
        &lt;% end %&gt;
        &lt;/ul&gt;
      &lt;/div&gt;
    &lt;% end %&gt;
  
    &lt;div class="field"&gt;
      &lt;%= f.label :position %&gt;&lt;br&gt;
      &lt;%= f.text_field :position %&gt;
    &lt;/div&gt;
    &lt;div class="field"&gt;
      &lt;%= f.label :date %&gt;&lt;br&gt;
      &lt;%= f.date_select :date %&gt;
    &lt;/div&gt;
    &lt;div class="field"&gt;
      &lt;%= f.label :start %&gt;&lt;br&gt;
      &lt;%= f.time_select :start %&gt;
    &lt;/div&gt;
    &lt;div class="field"&gt;
      &lt;%= f.label :end %&gt;&lt;br&gt;
      &lt;%= f.time_select :end %&gt;
    &lt;/div&gt;
    &lt;div class="field"&gt;
      &lt;%= f.label :description %&gt;&lt;br&gt;
      &lt;%= f.text_area :description %&gt;
    &lt;/div&gt;
  
    &lt;div class="actions"&gt;
      &lt;%= f.submit %&gt;
    &lt;/div&gt;
  &lt;% end %&gt;
  </code></pre>