Current time in Japan

Date.prototype.addHours = function (h) {
  this.setHours(this.getHours() + h);
  return this;
}

var japanTimeOffset = 9;
var timeZoneOffset = new Date().getTimezoneOffset() / 60;

var japanCurrentTIme = new Date().addHours(japanTimeOffset + timeZoneOffset);
var inWorkingHours = japanCurrentTIme.getHours() >= 8 && japanCurrentTIme.getHours() < 20;

console.log('Japan current time --> ' + japanCurrentTIme.toTimeString());
console.log('Japan bussines hours --> ' + inWorkingHours);