function update(datetime = "2017-01-01 05:11:58") {
var theevent = new Date(datetime);
now = new Date();
var sec_num = (theevent - now) / 1000;
var days = Math.floor(sec_num / (3600 * 24));
var hours = Math.floor((sec_num - (days * (3600 * 24)))/3600);
var minutes = Math.floor((sec_num - (days * (3600 * 24)) - (hours * 3600)) / 60);
var seconds = Math.floor(sec_num - (days * (3600 * 24)) - (hours * 3600) - (minutes * 60));
if (hours < 10) {hours = "0"+hours;}
if (minutes < 10) {minutes = "0"+minutes;}
if (seconds < 10) {seconds = "0"+seconds;}
return days+':'+ hours+':'+minutes+':'+seconds;
}