Set End Date input field to Start Date

I’m trying to set an end date field to the start date when that field is updated but it’s not working. Here’s what I have…

<input type="text" class="form-control" id="inp_start" name="start" aria-describedby="inp_start_help" placeholder="Enter Start" is="dmx-date-picker" timepicker="" minutes-increment="15" format="MM/DD/YYYY HH:mm" dmx-on:apply="modal_tripbit_add.sc_add.inp_end.setValue(value)">

<input type="text" class="form-control" id="inp_end" name="end" aria-describedby="inp_end_help" placeholder="Enter End" is="dmx-date-picker" format="MM/DD/YYYY HH:mm" timepicker="" minutes-increment="15">

Nothing happens. There’s no error.