window.onload = function(){
var url=[];
url[0] = 'BG_SaikiLand02.jpg';
url[1] = 'BG_SaikiLand04.jpg';
var elm = document.getElementById('SaikiLand');
h = (new Date()).getHours();
if((h >= 0) && (h < 6)) elm.style.backgroundImage = 'url(asset/' + url[1] + ')';
if((h >= 6) && (h < 12)) elm.style.backgroundImage = 'url(asset/' + url[0] + ')';
if((h >= 12) && (h < 18)) elm.style.backgroundImage = 'url(asset/' + url[0] + ')';
if((h >= 18) && (h < 24)) elm.style.backgroundImage = 'url(asset/' + url[1] + ')';
}