Convert date to another timezone in JavaScript

Question

I am looking for a function to convert date in one timezone to another.

It need two parameters,

• date (in format \"2012/04/10 10:10:30 +0000\")

Answer 1

I recently did this in Typescript :

// fromTimezone example : Europe/Paris, toTimezone example: Europe/London
private calcTime( fromTimezone: string, toTimezone: string, dateFromTimezone: Date ): Date {
  const dateToGetOffset = new Date( 2018, 5, 1, 12 );

  const fromTimeString = dateToGetOffset.toLocaleTimeString( "en-UK", { timeZone: fromTimezone, hour12: false } );
  const toTimeString = dateToGetOffset.toLocaleTimeString( "en-UK", { timeZone: toTimezone, hour12: false } );

  const fromTimeHours: number = parseInt( fromTimeString.substr( 0, 2 ), 10 );
  const toTimeHours: number = parseInt( toTimeString.substr( 0, 2 ), 10 );

  const offset: number = fromTimeHours - toTimeHours;

  // convert to msec
  // add local time zone offset
  // get UTC time in msec
  const dateFromTimezoneUTC = Date.UTC( dateFromTimezone.getUTCFullYear(),
    dateFromTimezone.getUTCMonth(),
    dateFromTimezone.getUTCDate(),
    dateFromTimezone.getUTCHours(),
    dateFromTimezone.getUTCMinutes(),
    dateFromTimezone.getUTCSeconds(),
  );

  // create new Date object for different city
  // using supplied offset
  const dateUTC = new Date( dateFromTimezoneUTC + ( 3600000 * offset ) );

  // return time as a string
  return dateUTC;
}

I Use "en-UK" format because it is a simple one. Could have been "en-US" or whatever works.

If first argument is your locale timezone and seconde is your target timezone it returns a Date object with the correct offset.