var myTimeout;
myTimeout = window.setTimeout("showTime();", 1000);

var parisOffset = 2;
var londonOffset = 1;
var newYorkOffset = -4;

function getRealHours(hours) {
	if (hours > 24) {
		return hours-24;
	}
	if (hours < 0) {
		return hours + 24;
	}
	return hours;
}

function showTime() {
    myTimeout = window.setTimeout("showTime();", 5000);

    myTime = new Date();
    var myGMTHours = myTime.getHours() + myTime.getTimezoneOffset()/60;
	
    var myMinutes;
    if (myTime.getMinutes() < 10) {
        myMinutes = '0' + myTime.getMinutes();
    } else {
        myMinutes = myTime.getMinutes();
    }
	
	var parisTimeHours = myGMTHours + parisOffset;
	var londonTimeHours = myGMTHours + londonOffset;
	var newYorkTimeHours = myGMTHours + newYorkOffset;

    window.document.getElementById("parisTimeSpan").innerHTML = getRealHours(parisTimeHours) + ":" + myMinutes;
    window.document.getElementById("londonTimeSpan").innerHTML = getRealHours(londonTimeHours) + ":" + myMinutes;
    window.document.getElementById("newYorkTimeSpan").innerHTML = getRealHours(newYorkTimeHours) + ":" + myMinutes;
    
}