date_interval.js

var date1 = new Date()
var date2 = new Date(2016, 10, 6); // Date(2016, 10, 6) is Nov. 6, 2016
var data1_ms = date1.getTime();
var data2_ms = date2.getTime();

// Then, calculate the milliseconds difference between the two dates.
var difference_ms = date2_ms - date1_ms;

// Finally, convert the difference back to days in which we should 
// divide the milliseconds by one day’s milliseconds:
var oneday = 1000 * 60 * 60 * 24;

// Math.ceil() makes the difference rational
var result = Math.ceil(differencems/one_day);