window.onload = function() {
var delay = 1000;
setInterval(function() {
change();
}, delay);
};
function change(){
var spHour_start = 6; // 開始時
var spHour_end = 22; // 終了時
var now = new Date();
var theHour = now.getHours();
// 期間内か判断
var cssFile = ((spHour_start <= theHour && theHour < spHour_end) ? "master.css" : "masterpm.css");
document.getElementById('basic').href=cssFile;
}