can't add a book because of form validation error

[adnoh]

when trying to add a book it returns me a form validation error.
not shure what was your plan, but currently you submit the date converted to timeformat (example: 1394838000000) and your entity wants a dateFormat which is not compatible by default.
I've tried with setup the formtype:
->add('releaseDate', 'datetime' ,array('date_widget'=> 'single_text', 'date_format'=>'yyyy-MM-dd', 'input'=>'timestamp'))
or
->add('releaseDate', 'datetime' ,array('date_widget'=> 'single_text', 'input'=>'timestamp'))
but this all did'nt work.
Tried even to divide by 1000 in the library.js function addBook #48 which seems to be a correct js-timestamp format to me.
still can't submit a book when releaseDate is filled.