title: Why is moment-timezone using a lot less space with webpack 4 and/or create react app 4?
body: <p>With webpack 3, I was using <a href="https://www.npmjs.com/package/moment-timezone-data-webpack-plugin" rel="nofollow noreferrer">moment-timezone-data-webpack-plugin</a> to reduce my bundle size and it worked well. Tests showed it reduced the bundle size dramatically. I've now upgraded to webpack 4 and create-react-app 4, and it seems like</p>
  <ol>
  <li>this plugin has no impact on the total bundle size</li>
  <li>analyzing the bundle, moment-timezone only takes about 7k</li>
  </ol>
  <p>As far as I can tell moment-timezone is functioning correctly in my app, so I'm very confused.</p>
  <p>Webpack 4 is a lot better at reducing bundle size, but there's no way it can know which timezone data my app needs are runtime, so I can't imagine how that could be part of the answer.</p>