function changeBackground() {

	if (!isNight()) {
		return;
	}

	header = document.getElementById("Header");
	if (!header) {
		return;
	}

	myCosmos = document.getElementById("Mycosmos");
	if (myCosmos == undefined) {
		return;
	}

	className = myCosmos.className;
	if ((className == "Blog")||((className == "Community"))) {
		return;
	}

	if (className == "Hana") {
		header.style.background = "url(/image/mod_header/bg_flower_night.gif) #fff left 37px no-repeat";
		return;
	}

	if (className == "Shoku") {
		header.style.background = "url(/image/mod_header/bg_gourmet_night.gif) #fff left 37px no-repeat";
		return;
	}

	if (className == "Sora") {
		header.style.background = "url(/image/mod_header/bg_sky_night.gif) #fff left 37px no-repeat";
		return;
	}

	header.style.background = "url(/image/mod_header/bg_all_night.gif) #fff left 37px no-repeat";
	return;
}

function isNight() {
	date = new Date();
	hours = date.getHours();
	if ((hours < 7)||(hours >= 19)) {
		return true;
	} else {
		return false;
	}
}