We also encountered such a problem when using JS. Later, after modification, the following code is available in the IE8 environment.
js end time-start time, get the number of days
function getDays(strDateStart,strDateEnd){
var strSeparator = "-"; //Date separator
var oDate1;
var oDate2;
var iDays;
oDate1= strDateStart .split(strSeparator);
oDate2= strDateEnd.split(strSeparator);
var strDateS = new Date(oDate1[0], oDate1[1]-1, oDate1[2]);
var strDateE = new Date(oDate2[0], oDate2[1]-1, oDate2[2]);
iDays = parseInt(Math.abs(strDateS - strDateE ) / 1000 / 60 / 60 /24)//Difference Convert milliseconds to days
return iDays ;
}