```javascriptfunction show_date_time() {

window.setTimeout(show_date_time, 1000);

var BirthDay = new Date("2/02/2020");

var today = new Date();

var timeold = today.getTime() - BirthDay.getTime();

var sectimeold = timeold / 1000;

var secondsold = Math.floor(sectimeold);

var msPerDay = 24 * 60 * 60 * 1000;

var e_daysold = timeold / msPerDay;

var daysold = Math.floor(e_daysold);

e_hrsold = (daysold - e_daysold) * -24;

hrsold = Math.floor(e_hrsold);

e_minsold = (hrsold - e_hrsold) * -60;

minsold = Math.floor((hrsold - e_hrsold) * -60);

e_seconds = (minsold - e_minsold) * -60;

e_seconds = Math.floor((hrsold - e_hrsold) * -60);

e_seconds = Math.floor((minsold - e_minsold) * -60);

e_seconds = Math.floor(sectimeold % (24 * 3600));

e_seconds = Math.floor(e_seconds * (-1));

span_dt_dt.innerHTML = daysold + "天" + hrsold + "小时" + minsold + "分" + secondsold + "秒";

}

show_date_time();

```