title: Input_formats to DateTimeField
body: <p>I have a DateTimeField :</p>
  
  <pre><code> start_time=forms.DateTimeField(input_formats='%y-%m-%d %H:%M')
  </code></pre>
  
  <p>and in html</p>
  
  <pre><code>   {{form.start_time}}
  </code></pre>
  
  <p>but no matter what i entre in th field, like: 2013-07-07 19:00
  it will always give me an error : enter valid date/time, what is worng here? Thanks in Advance</p>