title: symfony2 - date choice input renders timestamp instead of month name
body: <p>I just recently ran into a problem, where my Symfony2 app renders form with invalid date choice input. Specifically, it renders the "month" select with numbers inside, instead of month names.</p>
  
  <p>The definition of the form type goes like this:</p>
  
  <pre><code>$builder
          -&gt;add('title')
          -&gt;add('shortcut')
          -&gt;add('description')
          -&gt;add('category')
          -&gt;add('release_date', 'date', array(
              'input' =&gt; 'datetime',
              'widget' =&gt; 'choice'
          ));
  </code></pre>
  
  <p>This definition then (by using form_widget in Twig) renders the following for month select:</p>
  
  <pre><code>&lt;select id="nucleo_gamesbundle_gametype_release_date_month" name="nucleo_gamesbundle_gametype[release_date][month]" required="required"&gt;
    &lt;option value="1"&gt;1326585600&lt;/option&gt;
    &lt;option value="2"&gt;1329264000&lt;/option&gt;
    &lt;option value="3"&gt;1331769600&lt;/option&gt;
    &lt;option value="4"&gt;1334448000&lt;/option&gt;
    &lt;option value="5"&gt;1337040000&lt;/option&gt;
    &lt;option value="6"&gt;1339718400&lt;/option&gt;
    &lt;option value="7"&gt;1342310400&lt;/option&gt;
    &lt;option value="8"&gt;1344988800&lt;/option&gt;
    &lt;option value="9"&gt;1347667200&lt;/option&gt;
    &lt;option value="10"&gt;1350259200&lt;/option&gt;
    &lt;option value="11"&gt;1352937600&lt;/option&gt;
    &lt;option value="12"&gt;1355529600&lt;/option&gt;
  &lt;/select&gt;
  </code></pre>
  
  <p>Does anyone know, how to force Symfony to render option texts as month names (eg. January, February, etc.)? Thank you very much.</p>
  
  <p><strong>EDIT:</strong>
  Twig template (the form part) looks like this:</p>
  
  <pre><code>&lt;form action="{{ path('game_admin_update', {'id' : entity.id}) }}" method="post" class="form" {{ form_enctype(edit_form) }}&gt;
    &lt;fieldset&gt;
      &lt;div class="widget"&gt;
          &lt;div class="title"&gt;&lt;img src="{{ asset('admin/images/icons/dark/list.png') }}" alt="" class="titleIcon" /&gt;&lt;h6&gt;Základní informace&lt;/h6&gt;&lt;/div&gt;
          &lt;div class="formRow"&gt;
              {{ form_label(edit_form.title, 'form.game.title'|trans({},'admin')) }}
              &lt;div class="formRight"&gt;{{ form_widget(edit_form.title) }}&lt;/div&gt;
              &lt;div class="clear"&gt;&lt;/div&gt;
          &lt;/div&gt;
          &lt;div class="formRow"&gt;
              {{ form_label(edit_form.shortcut, 'form.game.shortcut'|trans({},'admin')) }}
              &lt;div class="formRight"&gt;{{ form_widget(edit_form.shortcut) }}&lt;/div&gt;
              &lt;div class="clear"&gt;&lt;/div&gt;
          &lt;/div&gt;
          &lt;div class="formRow"&gt;
              {{ form_label(edit_form.description, 'form.game.description'|trans({},'admin')) }}
              &lt;div class="formRight"&gt;{{ form_widget(edit_form.description, { 'attr': {'class': 'richEditor'} }) }}&lt;/div&gt;
              &lt;div class="clear"&gt;&lt;/div&gt;
          &lt;/div&gt;
          &lt;div class="formRow"&gt;
              {{ form_label(edit_form.release_date, 'form.game.release_date'|trans({},'admin')) }}
              &lt;div class="formRight"&gt;{{ form_widget(edit_form.release_date) }}&lt;/div&gt;
              &lt;div class="clear"&gt;&lt;/div&gt;
          &lt;/div&gt;
          {{ form_rest(edit_form) }}
          &lt;div class="formSubmit"&gt;&lt;input type="submit" value="{{ 'form.game.submit.edit'|trans({},'admin') }}" class="greenB" /&gt;&lt;/div&gt;
          &lt;div class="clear"&gt;&lt;/div&gt;
      &lt;/div&gt;
  &lt;/fieldset&gt;
  </code></pre>
  
  <p></p>
  
  <p>So nothing special there</p>