jQuery特定日期全站變灰

在一些特殊的日子里，我們可能會用到這段代碼。
 

<script>
$(document).ready(function() {
    var today = new Date();
    var todayMonth = today.getMonth() + 1;
    var todayDate = today.getDate();
function gray(){
 $('body').css({
     "-webkit-filter":"grayscale(100%)",
     "-moz-filter":"grayscale(100%)",
     "-ms-filter":"grayscale(100%)",
     "-o-filter":"grayscale(100%)",
     "filter":"progid:DXImageTransform.Microsoft.BasicImage(grayscale=1)",
     "_filter":"none"});
};
    if (todayMonth == 4 && todayDate == 4) {gray()}; // 4 月 4 日
    if (todayMonth == 6 && todayDate == 4) {gray()};
    if (todayMonth == 12 && todayDate == 13) {gray()}; // 12 月 13 日
})
</script>