Date fields allow to enter random numbers

Hello there,
We have some date fields in our metabox and just realised it is possible to enter and save random numbers in the field. Is there some built-in way to enable validation and disallow the entry of dates in the wrong format?

Here's how we are defining one of the affected date fields.

Thanks,
Mauro.

array (
                'id' => 'availability_start',
                'type' => 'date',
                'format'=>'mm/dd/yy',
                'name' => 'Available From',
                'desc' => 'Will be available starting on this date.',
            ),