auto_gray.html

<style>
    body.grayDay { 
        filter: progid:DXImageTransform.Microsoft.BasicImage(grayscale=1); 
        -webkit-filter: grayscale(100%); }
</style>
<script>
    window.onload = function() {
    var grayDay = [108, 207, 219, 404, 420, 512, 815, 909, 918, 1213];
    var today = new Date();
    var d = (today.getMonth() + 1) * 100 + today.getDate();
    grayDay.forEach(function(i) {
      if (i == d) {
        var classVal = document.getElementsByTagName('body')[0].getAttribute("class");
        classVal = classVal.concat(" grayDay");
        document.getElementsByTagName('body')[0].setAttribute("class", classVal);
      }
    });
  }
</script>

/*
 *
 * 纪念那些平凡而伟大的小人物，死亡不是生命的终点，遗忘才是。
 *
 */

Date.prototype.format = function (fmt) {
    var o = {
        "M+": this.getMonth() + 1, //月份
        "d+": this.getDate(), //日
        "h+": this.getHours(), //小时
        "m+": this.getMinutes(), //分
        "s+": this.getSeconds(), //秒
        "q+": Math.floor((this.getMonth() + 3) / 3), //季度
        "S": this.getMilliseconds() //毫秒
    };
    if (/(y+)/.test(fmt)) fmt = fmt.replace(RegExp.$1, (this.getFullYear() + "").substr(4 - RegExp.$1.length));
    for (var k in o)
        if (new RegExp("(" + k + ")").test(fmt)) fmt = fmt.replace(RegExp.$1, (RegExp.$1.length == 1) ? (o[k]) : (("00" + o[k]).substr(("" + o[k]).length)));
    return fmt;
}

let datelist = {
    "02-08": "2020-02-06 21:30分，李文亮医生的心脏停止了跳动，疫情的“吹哨人”，谢谢你曾尝试拯救地球。"
};

(() => {
    let nowday = (new Date()).format("MM-dd");
    if (nowday in datelist) {
        // 根据实际情况修改样式
        document.getElementById("idx-msg").innerHTML = datelist[nowday];
        document.getElementById("idx-emoji").innerHTML = "";
        document.getElementById("idx-img").src = "";
        document.getElementById("idx-img").style.filter = 'grayscale(100%)';
    }
})();