In Magento 2 you can add Datepicker for a custom option Date Field in Product detail page using enable Javascript Calander. Native Magento doesn’t display Date picker for Date Custom Option field. They just show as a Dropdown option for Day, Month and Year.
You have to enable Javascript Calander from System Configuration.
I have a question regarding Magento 2 date format, can we change the date format though out the website in a same format like dd/mm/yyyy?