How to change maker icon - google-maps-api-3

Question

I want to change the marker icon when the clock reaches 10 PM and go back to same icon when 6 AM .. how do I pick the right time of the clock from somewhere? and how to put the icon to change such a time
thanks !!
my code
function initialize() {
var mapDiv = document.getElementById('map-canvas');
var map = new google.maps.Map(mapDiv, {
center: new google.maps.LatLng(-22.968015,-43.183161),
zoom: 16,
mapTypeId: google.maps.MapTypeId.ROADMAP });
var green = 'images/VERDE.png';
var yellow = 'images/AMARELO.png';
var red = 'images/VERMELHA.png';
var marker = new google.maps.Marker({
map: map,
position: new google.maps.LatLng(-22.967311,-43.186073),
icon: green});

Answer 1

The following code changes the the marker according to time.
var now=new Date().getUTCHours();
now -= 2;//Set for Rio Adjust to your time zone
var startTime = 22;//10 PM
var finishTime = 6;//6 AM
var icon;
function initialize() {
var mapDiv = document.getElementById('map');
var map = new google.maps.Map(mapDiv, {
center: new google.maps.LatLng(-22.968015,-43.183161),
zoom: 16,
mapTypeId: google.maps.MapTypeId.ROADMAP });
var green = 'images/green.png';
var yellow = 'images/yellow.png';
var red = 'images/red.png';
//Choosing icon by time
if(now >= finishTime&&now < startTime){
icon = green;
}else {
icon = red;
}
var marker = new google.maps.Marker({
map: map,
position: new google.maps.LatLng(-22.967311,-43.186073),
icon: icon});
}
Points to note.
Only works in one time zone.
You will need to alter now -= 2 to suit local time with winter saving if required.
The boundry values may require tuning.