// Is this the Entries index page?
if (Craft.elementIndex && Craft.elementIndex.elementType === 'craft\\elements\\Entry') {
    // Add a date range picker to the toolbar
    let startDate = endDate = null;
    Craft.ui.createDateRangePicker({
        onChange: function(s, e) {
            startDate = s;
            endDate = e;
            Craft.elementIndex.updateElements();
        },
    }).appendTo(Craft.elementIndex.$toolbar);

    // When the element index is updated, set our Date/Time field param
    Craft.elementIndex.on('registerViewParams', function(event) {
        event.params.criteria.myDateTimeField = ['and'];
        if (startDate) {
            event.params.criteria.myDateTimeField.push('>=' + (startDate.getTime() / 1000));
        }
        if (endDate) {
            event.params.criteria.myDateTimeField.push('<' + (endDate.getTime() / 1000 + 86400));
        }
    });
}