If you have a lot of date operations, you can use momentjs, as mentioned by previous responses (Like date comparison, modification, localisation etc).
You may use the native javascript date object if you merely want to display the date as a string.
var event = new Date();
console.log(event.toLocaleString('en-GB', { timeZone: 'Europe/London' }));
You've already done some of it. Simply supply "timeZone" information to your toLocalseString function.