How to get Australia Sydney timezone offset in javascript nodejs

Question

Austalia/Sydney timezone offset (UTC to AEST difference) is +10:00 (from April first Sunday) and +11:00 (from April first Sunday) (from October first Sunday).

There is a 600 minute or 660 minute difference.

In javascript/nodejs/momentjs, how can I retrieve the time difference? Regardless of server time?

Answer 1

I haven't done any study to find out whether there is a "better" method to accomplish this, but then why would I?

This function was written in a matter of minutes using Intl.DateTimeFormat

Modern browsers and nodejs are supported.

function getTZoffset(timeZone, d, m, y) {
  const date = Date.UTC(y, m - 1, d, 0, 0, 0);
  const tgt = Intl.DateTimeFormat('en', { timeZone, dateStyle: "short", timeStyle: 'short', hour12: false }).format(date).split(',');
  const utc = Intl.DateTimeFormat('en', { timeZone: 'UTC', dateStyle: "short" }).format(date).split(',');
  const tgtTimes = tgt[1].split(':').map(Number);
  const tgtTime = (tgtTimes[0] % 24) * 60 + tgtTimes[1]
  const utcTime = tgt[0] === utc[0] ? 0 : 24 * 60;
  return tgtTime - utcTime;
}

for (let m = 1; m <= 12; m++) {
  console.log(`Sydney/Australia 1/${m}/2020: ${getTZoffset('Australia/Sydney', 1, m, 2020)}`);
}
for (let m = 1; m <= 12; m++) {
  console.log(`America/New_York 1/${m}/2020: ${getTZoffset('America/New_York', 1, m, 2020)}`);
}