1const date1 = new Date('7/13/2010');
2const date2 = new Date('12/15/2010');
3console.log(getDifferenceInDays(date1, date2));
4console.log(getDifferenceInHours(date1, date2));
5console.log(getDifferenceInMinutes(date1, date2));
6console.log(getDifferenceInSeconds(date1, date2));
7
8function getDifferenceInDays(date1, date2) {
9  const diffInMs = Math.abs(date2 - date1);
10  return diffInMs / (1000 * 60 * 60 * 24);
11}
12
13function getDifferenceInHours(date1, date2) {
14  const diffInMs = Math.abs(date2 - date1);
15  return diffInMs / (1000 * 60 * 60);
16}
17
18function getDifferenceInMinutes(date1, date2) {
19  const diffInMs = Math.abs(date2 - date1);
20  return diffInMs / (1000 * 60);
21}
22
23function getDifferenceInSeconds(date1, date2) {
24  const diffInMs = Math.abs(date2 - date1);
25  return diffInMs / 1000;
26}

1const diffDays = (date, otherDate) => Math.ceil(Math.abs(date - otherDate) / (1000 * 60 * 60 * 24));
2
3// Example
4diffDays(new Date('2014-12-19'), new Date('2020-01-01'));   // 1839

1const date1 = new Date('7/13/2010');
2const date2 = new Date('12/15/2010');
3const diffTime = Math.abs(date2 - date1);
4const diffDays = Math.ceil(diffTime / (1000 * 60 * 60 * 24)); 
5console.log(diffTime + " milliseconds");
6console.log(diffDays + " days");

1/* difference between date1 and date2 in days (date2 - date1) */
2/* date1 and date 2 are already javascript date objects */
3function dateDifference(date2, date1) {
4    const _MS_PER_DAY = 1000 * 60 * 60 * 24;
5
6    // Discard the time and time-zone information.
7    const utc1 = Date.UTC(date1.getFullYear(), date1.getMonth(), date1.getDate());
8    const utc2 = Date.UTC(date2.getFullYear(), date2.getMonth(), date2.getDate());
9
10    return Math.floor((utc2 - utc1) / _MS_PER_DAY);
11}

1var date1 = new Date();    
2 var date2 = new Date("2025/07/30 21:59:00");
3  
4showDiff(date1,date2);
5
6function showDiff(date1, date2){
7
8    var diff = (date2 - date1)/1000;
9    diff = Math.abs(Math.floor(diff));
10
11    var days = Math.floor(diff/(24*60*60));
12    var leftSec = diff - days * 24*60*60;
13
14    var hrs = Math.floor(leftSec/(60*60));
15    var leftSec = leftSec - hrs * 60*60;
16
17    var min = Math.floor(leftSec/(60));
18    var leftSec = leftSec - min * 60;
19	console.info("You have " + days + " days " + hrs + " hours " + min + " minutes and " + leftSec + " seconds");
20   
21    return {
22        d: days,
23        h: hrs,
24        i: min,
25        s: leftSec
26    };
27}

1var DateDiff = {
2
3    inDays: function(d1, d2) {
4        var t2 = d2.getTime();
5        var t1 = d1.getTime();
6
7        return parseInt((t2-t1)/(24*3600*1000));
8    },
9
10    inWeeks: function(d1, d2) {
11        var t2 = d2.getTime();
12        var t1 = d1.getTime();
13
14        return parseInt((t2-t1)/(24*3600*1000*7));
15    },
16
17    inMonths: function(d1, d2) {
18        var d1Y = d1.getFullYear();
19        var d2Y = d2.getFullYear();
20        var d1M = d1.getMonth();
21        var d2M = d2.getMonth();
22
23        return (d2M+12*d2Y)-(d1M+12*d1Y);
24    },
25
26    inYears: function(d1, d2) {
27        return d2.getFullYear()-d1.getFullYear();
28    }
29}
30
31var dString = "May, 20, 1984";
32
33var d1 = new Date(dString);
34var d2 = new Date();
35
36document.write("<br />Number of <b>days</b> since "+dString+": "+DateDiff.inDays(d1, d2));
37document.write("<br />Number of <b>weeks</b> since "+dString+": "+DateDiff.inWeeks(d1, d2));
38document.write("<br />Number of <b>months</b> since "+dString+": "+DateDiff.inMonths(d1, d2));
39document.write("<br />Number of <b>years</b> since "+dString+": "+DateDiff.inYears(d1, d2));