У вашего броузера проблема в совместимости с HTML5
MySQL DATETIME type is used for values that contain both date and time parts. MySQL retrieves and displays DATETIME values in 'YYYY-MM-DD HH:MM:SS'.
This video shows you how to verify date input format is 'YYYY-MM-DD HH:MM:SS', i.e."Y-m-d H:i:s" in PHP in HTML form.
More about this video:
http://jiansenlu.blogspot.ca/2013/09/php-verify-input-date-format.html