npm install moment-timezone

var moment = require('moment-timezone');
moment().tz("America/Los_Angeles").format();

Note: By default, webpack bundles all moment-timezone data (in moment-timezone 0.5.25, that’s over 900 KBs minified). To strip out unwanted data and bundle only the zone and date range data you need, add the moment-timezone-data-webpack-plugin package:

// webpack.config.js
const MomentTimezoneDataPlugin = require('moment-timezone-data-webpack-plugin');
const currentYear = new Date().getFullYear();

module.exports = {
    plugins: [
        // To include only specific zones, use the matchZones option
        new MomentTimezoneDataPlugin({
            matchZones: /^America/
        }),

        // To keep all zones but limit data to specific years, use the year range options
        new MomentTimezoneDataPlugin({
            startYear: currentYear - 5,
            endYear: currentYear + 5,
        }),
    ],
};

Alternatively, the pre-built bundles are also included in the npm package, and can be loaded directly. See the Node.js section for more details.

Also see the primary Moment.js Webpack documentation for an example of how to reduce Moment’s bundled locale data. Together these techniques can significantly reduce the final bundle size (by over 1 MB minified, or 85 KB minified + gzipped).