A Javascript method to determine the timezone of the browser.

Timezone.js

function getTimezoneName() {
  const today = new Date();
  const short = today.toLocaleDateString(undefined);
  const full = today.toLocaleDateString(undefined, { timeZoneName: 'short' });  // Trying to remove date from the string in a locale-agnostic way
  const shortIndex = full.indexOf(short);
  if (shortIndex >= 0) {
    const trimmed = full.substring(0, shortIndex) + full.substring(shortIndex + short.length);    // by this time `trimmed` should be the timezone's name with some punctuation -
    // trim it from both sides
    return trimmed.replace(/^[\s,.\-:;]+|[\s,.\-:;]+$/g, '');  } 
  else {
    // in some magic case when short representation of date is not present in the long one, just return the long one as a fallback, since it should contain the timezone's name
    return full;
  }
}