title: moment.js change locale not working
body: <p>My project is a react project. </p>
  
  <p>My website is a mutilanguage website, when I change the web language. <code>moment.locale(lang)</code> not working.</p>
  
  <p>My code is:</p>
  
  <pre class="lang-js prettyprint-override"><code>const startDate = moment.utc(start).locale(lang);
  const endDate = moment.utc(end).locale(lang);
  </code></pre>
  
  <p>whatever I set <code>lang</code> I check the <code>startDate.locale()</code> always is <code>'en'</code>
  <code>startDate.format('ll')</code> result always is English.</p>