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,

<div class="field required" id="daterange">
    <label for="from" class="label">
        <span>From date</span>
    </label>
    <div class="control">
        <input class="input-text required-entry"
            type="text"
            id="from-date"
            name="from-date" style="width: 500px"/>
    </div>
    <label for="to" class="label">
        <span>To date</span>
    </label>
    <div class="control">
        <input class="input-text required-entry"
            type="text"
            id="to-date"
            name="to-date" style="width: 500px" />
    </div>
</div>

<script>
require([
    'jquery',
    'mage/calendar'
], function($){
    $('#daterange').dateRange({
        buttonText: 'Choose Date',
        from: {
            id: 'from-date'
        },
        to: {
            id: 'to-date'
        }
    });
});
</script>