function setWeekColor() {
    var calendar = document.getElementById('wp-calendar');
    if (!calendar) return;
    var th = calendar.getElementsByTagName('th');
    for (i = 0; i < th.length; i++) {
        if (th[i].getAttribute('title') == '日曜日') { th[i].className = 'holiday'; }
        if (th[i].getAttribute('title') == '木曜日') { th[i].className = 'holiday'; }
        if (th[i].getAttribute('title') == '土曜日') {  th[i].className = 'saturday'; }
    }
}