Date / Datetime field with clone and timestamp wont work

Hello,
i have a datetime / date field with a clone parameter.
When i set the field 'timestamp' => true, the functionally wont work.

array(
	'name'          => __('Date'),
	'id'            => 'my_post_type_dates',
	'type'          => 'date',
	'js_options'    => array('dateFormat' => 'dd.mm.yy'),
	'timestamp'     => true,
	'clone'         => true
)

Thank you