// function to calculate local time
// in a different city
// given the city's UTC offset
function calcTime(city, offset) {

    // create Date object for current location
    d = new Date();
   
    // convert to msec
    // add local time zone offset
    // get UTC time in msec
    utc = d.getTime() + (d.getTimezoneOffset() * 60000);
   
    // create new Date object for different city
    // using supplied offset
    nd = new Date(utc + (3000000*offset));
   
    // return time as a string
    return "" + city + "" + nd.toLocaleString();

}



// get London time
document.write (calcTime('', '-6'));