Setup a bootstrap datepicker Synchronized dt_start and dt_end

datepicker.js

#http://makitweb.com/how-to-add-datepicker-in-bootstrap/
#https://uxsolutions.github.io/bootstrap-datepicker/?markup=input&format=&weekStart=&startDate=&endDate=&startView=0&minViewMode=0&maxViewMode=4&todayBtn=false&clearBtn=false&language=en&orientation=auto&multidate=&multidateSeparator=&keyboardNavigation=on&forceParse=on#sandbox
#https://github.com/uxsolutions/bootstrap-datepicker/blob/master/docs/options.rst
#https://bootstrap-datepicker.readthedocs.io/en/latest/options.html#startdate

#Sync dt_start with dt_end

<div class="form-group">
    <label class="form-check-label">Date Range<br>
        <div>
            <div id="event_period">
                <input id='dt_start' data-date-start-date="-Infinity" style="width:100px;margin: 0em 2em 1em 0em;"  type="text" class="datepicker picker-only" readonly placeholder="Select date" data-provide="datepicker" data-date="<?php echo date("Y-m-d"); ?>" value="<?php echo date("Y-m-d"); ?>" data-date-format="yyyy-mm-dd" />To
                <input id='dt_end'   data-date-end-date="Infinity"    style="width:100px;margin: 0em 2em 1em 2em;"  type="text" class="datepicker picker-only" readonly placeholder="Select date" data-provide="datepicker" data-date="<?php echo date("Y-m-d"); ?>" value="<?php echo date("Y-m-d"); ?>" data-date-format="yyyy-mm-dd" />
            </div>
        </div>
    </label>
</div>



$('#dt_start').datepicker()
        .on('changeDate', function(e) {
            var dt_start = $('#dt_start').datepicker('getDate');
            $('#dt_end').datepicker('setStartDate', dt_start);
        });

 $('#dt_end').datepicker()
        .on('changeDate', function(e) {
            var dt_end = $('#dt_end').datepicker('getDate');
            $('#dt_start').datepicker('setEndDate', dt_end);
        });