Magento 2 Display Date Range field in Custom form.

You can add custom Date range field in your form using mage/calender widget of Magento.

DateRange field used for control two date range for a specific time.
DateRange widget used for Booking Return AirTicket, Train Ticket.

You can check for  Add Datepicker in custom form

Its also used for a show a Report for a specific time period.

You can add date range using below code,