How to get time difference based on timezone?

Question

I need to get time difference in hours and minutes of other user who is situated in anather country. Here is what i have done.

const timeZone = "Asia/tokyo"; // Time zone can be changed

let arr: any = new Date().toLocaleString("en-US", {
  timeZone: timeZone,
  dateStyle: "full",
  timeStyle: "full",
});

let currentTime = new Date();

Need to get difference between currentHour and arr

Answer 1

Firstly, use en-CA locale for the "calculation" ... it outputs yyyy-mm-dd hh:mm:ss which makes it simple to manipulate

Secondly, add hour12: false as you want 24 hour time

Then you can

const minutesToHHMM = (m) => {
  const s = m < 0 ? '-' : '';
  m = Math.abs(m);
  const mm = (m % 60).toString().padStart(2, 0);
  const hh = Math.floor(m / 60);
  return `${s}${hh}:${mm}`;
}
const timeZone = 'Australia/Eucla'; // odd timezone to always show minutes in difference
const date = new Date();
date.setMilliseconds(0); // remove millisecond since we are not creating the "other" time with milliseconds
const other = new Date(...date
  .toLocaleString('en-CA', {
    timeZone,
    hour12: false,
  })
  .replaceAll('-',':') // convert yyyy-mm-dd to yyyy:mm:dd
  .replaceAll(', ', ':') // add ':' between date and time
  .split(':') // split all the values
  .map((v,i) => v - (i===1)) // subtract one from month
);

console.log("other time", other.toLocaleString());
console.log("local time", date.toLocaleString());
console.log("difference", minutesToHHMM((other-date)/60000));

My Typescript is inelegant ... but

const minutesToHHMM = (m:number) => {
  const s = m < 0 ? '-' : '';
  m = Math.abs(m);
  const mm = (m % 60).toString().padStart(2, "0");
  const hh = Math.floor(m / 60);
  return `${s}${hh}:${mm}`;
}
const timeZone = 'Australia/Eucla'; // odd timezone to always show minutes in difference
const date = new Date();
date.setMilliseconds(0); // remove millisecond since we are not creating the "other" time with milliseconds

const other = new Date(...(date
  .toLocaleString('en-CA', {
      timeZone,
      hour12: false,
  })
  .replaceAll('-',':') // convert yyyy-mm-dd to yyyy:mm:dd
  .replaceAll(', ', ':') // add ':' between date and time
  .split(':') // split all the values
  .map(Number)
  .map((v:number, i:number) => v - ((i===1) ? 1 : 0)) as []) // subtract 1 from month
);

console.log("other time", other.toLocaleString());
console.log("local time", date.toLocaleString());
console.log("difference", minutesToHHMM((+other - +date)/60000));

Tried that on a TS Playground, seems to work