title: How to set the timezone on sonata_type_datetime_picker
body: <p>First question after using stackoverflow for years. Thanks for all the answers all over the years.</p>
  
  <p>I have an issue with the sonata_type_datetime_picker.</p>
  
  <p>My php.ini timezone is set to Europe/Paris.</p>
  
  <p>In my sonata admin, i have a form to set date-start and date-end for a voucher.</p>
  
  <pre><code>            -&gt;with('Conditions',['translation_domain' =&gt; 'SmallableAdminBundle'])
              -&gt;add('startAt', 'sonata_type_datetime_picker', [
                  'label' =&gt; 'form.commercialvoucher.startAt',
                  'translation_domain' =&gt; 'SmallableAdminBundle',
                  'format' =&gt; 'dd/MM/yyyy HH:mm',
                  'attr' =&gt; [
  
                  ],
              ])
              -&gt;add('endAt', 'sonata_type_datetime_picker', [
                  'label' =&gt; 'form.commercialvoucher.endAt',
                  'translation_domain' =&gt; 'SmallableAdminBundle',
                  'format' =&gt; 'dd/MM/yyyy HH:mm',
                  'attr' =&gt; [
  
                  ],
              ])
  </code></pre>
  
  <p>When i submit the form, seems the datetime are GMT time, so i lost basically one hour.</p>
  
  <p>Example : When i edit my voucher, change the dates and submit, here with 10h00, i get 9:00.</p>
  
  <pre><code>    CRUDController.php on line 362:
  CommercialVoucher {#241 ▼
        #id: 537287
        #code: "TEST_time"
        #name: "TEST_time"
        #description: "TEST_time"
        #validated: true
        #startAt: DateTime {#2791 ▼
          +"date": "2014-12-22 09:02:00.000000"
          +"timezone_type": 1
          +"timezone": "+00:00"
        }
        #endAt: DateTime {#2794 ▼
          +"date": "2014-12-22 09:00:00.000000"
          +"timezone_type": 1
          +"timezone": "+00:00"
        }
  </code></pre>
  
  <p>When i do another changes on the voucher, leaving the date unchanged, i get the right timezone.</p>
  
  <pre><code>    CRUDController.php on line 362:
  CommercialVoucher {#241 ▼
    #id: 537287
    #code: "TEST_time"
    #name: "TEST_time"
    #description: "TEST_time"
    #validated: true
    #startAt: DateTime {#1397 ▼
      +"date": "2014-12-22 09:02:00.000000"
      +"timezone_type": 3
      +"timezone": "Europe/Paris"
    }
    #endAt: DateTime {#1398 ▼
      +"date": "2014-12-22 09:00:00.000000"
      +"timezone_type": 3
      +"timezone": "Europe/Paris"
    }
  </code></pre>
  
  <p>I tried a lot in my voucher admin, using the option format, date_format. I tried also to set timezone in the sonata config, but nothing worked so far.</p>