Passing a day and a timezone offset and getting back local time.

dateTime.js

const getLocalTime = (date, offset) => {
  const utc = date.getTime() - (date.getTimezoneOffset() * 60000);
  const corrected = new Date(utc + (3600000 * offset));
  return {
    hours: corrected.getHours(),
    minutes: corrected.getMinutes(),
  };
};

// Tehran Local Time
getLocalTime(new Date(), '-4.5');