[TYPO3-english] extbase DateTime property mapping error in 6.1

[Domi]

Hello,

I use in 6.1 the new property mapper and want to save the DateTime with 
the native date picker and a fallback of jQuery.

/**
  * dateOfBirth
  *
  * @var \DateTime
  * @validate NotEmpty,DateTime
  */
protected $dateOfBirth;

In fluid:
<f:form.textfield
     property="dateOfBirth"
     value="{client.dateOfBirth->f:format.date(format: 'Y-m-d')}"
     required="TRUE"
     type="date" />

If I try to save my form I catch following error:

1307719788: The date "2012-12-02" was not recognized (for format 
"Y-m-d\TH:i:sP").

How do I set the property correctly?

Thanks,
Dominic