JSFiddle - React, Tailwind, and code Playground

HTML

<link rel="stylesheet" href="https://cdnjs.cloudflare.com/ajax/libs/twitter-bootstrap/3.3.7/css/bootstrap.min.css">
<link rel="stylesheet" href="https://cdnjs.cloudflare.com/ajax/libs/bootstrap-datepicker/1.6.4/css/bootstrap-datepicker.min.css">
<script src="https://cdnjs.cloudflare.com/ajax/libs/twitter-bootstrap/3.3.7/js/bootstrap.min.js"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/bootstrap-datepicker/1.6.4/js/bootstrap-datepicker.min.js"></script>
Start: <input type="text" id="event_start_date"/>
<br/>
Deadline: <input type="text" id="event_registration_deadline"/>

JavaScript

jQuery('input#event_start_date').datepicker({
            format : 'yyyy-mm-dd',
            autoclose : true,
            todayHighlight: true  
        }).on('changeDate', function(){
var aDayBefore = new Date(jQuery(this).val());
aDayBefore.setDate(aDayBefore.getDate()-1);            jQuery('#event_registration_deadline').datepicker('setEndDate', aDayBefore);
        });