这段代码将返回两个日期的差值(以天为单位):

const previous_date = new Date("2019-12-23");
const current_date = new Date();

const current_year = current_date.getFullYear();
const previous_date_year = 
previous_date.getFullYear();

const difference_in_years = current_year - 
previous_date_year;

let months = current_date.getMonth();
months = months + 1; // for making the indexing 
// of months from 1

for(let i = 0; i < difference_in_years; i++){
months = months + 12;
}

let days = current_date.getDate();

days = days + (months * 30.417);

console.log(`The days between ${current_date} and 
${previous_date} are : ${days} (approximately)`);

function DateDiff(b, e)
{
    let
        endYear = e.getFullYear(),
        endMonth = e.getMonth(),
        years = endYear - b.getFullYear(),
        months = endMonth - b.getMonth(),
        days = e.getDate() - b.getDate();
    if (months < 0)
    {
        years--;
        months += 12;
    }
    if (days < 0)
    {
        months--;
        days += new Date(endYear, endMonth, 0).getDate();
    }
    return [years, months, days];
}

[years, months, days] = DateDiff(
    new Date("October 21, 1980"),
    new Date("July 11, 2017")); // 36 8 20

另一种解决方案是将difference转换为一个新的Date对象，并获得该日期的年(与1970年不同)、月、日等。

var date1 = new Date(2010, 6, 17);
var date2 = new Date(2013, 12, 18);
var diff = new Date(date2.getTime() - date1.getTime());
// diff is: Thu Jul 05 1973 04:00:00 GMT+0300 (EEST)

console.log(diff.getUTCFullYear() - 1970); // Gives difference as year
// 3

console.log(diff.getUTCMonth()); // Gives month count of difference
// 6

console.log(diff.getUTCDate() - 1); // Gives day count of difference
// 4

所以差异就像“3年6个月零4天”。如果你想以一种人类可读的风格呈现不同，这将对你有所帮助。

var date1 = new Date("06/30/2019");
var date2 = new Date("07/30/2019");
  
// To calculate the time difference of two dates
var Difference_In_Time = date2.getTime() - date1.getTime();
  
// To calculate the no. of days between two dates
var Difference_In_Days = Difference_In_Time / (1000 * 3600 * 24);
  
//To display the final no. of days (result)
document.write("Total number of days between dates  <br>"
               + date1 + "<br> and <br>" 
               + date2 + " is: <br> " 
               + Difference_In_Days);

function DateDiff(date1, date2) {
    date1.setHours(0);
    date1.setMinutes(0, 0, 0);
    date2.setHours(0);
    date2.setMinutes(0, 0, 0);
    var datediff = Math.abs(date1.getTime() - date2.getTime()); // difference 
    return parseInt(datediff / (24 * 60 * 60 * 1000), 10); //Convert values days and return value      
}

var DateDiff = {
 
    inDays: function(d1, d2) {
        var t2 = d2.getTime();
        var t1 = d1.getTime();
 
        return Math.floor((t2-t1)/(24*3600*1000));
    },
 
    inWeeks: function(d1, d2) {
        var t2 = d2.getTime();
        var t1 = d1.getTime();
 
        return parseInt((t2-t1)/(24*3600*1000*7));
    },
 
    inMonths: function(d1, d2) {
        var d1Y = d1.getFullYear();
        var d2Y = d2.getFullYear();
        var d1M = d1.getMonth();
        var d2M = d2.getMonth();
 
        return (d2M+12*d2Y)-(d1M+12*d1Y);
    },
 
    inYears: function(d1, d2) {
        return d2.getFullYear()-d1.getFullYear();
    }
}
 
var dString = "May, 20, 1984";
 
var d1 = new Date(dString);
var d2 = new Date();
 
document.write("<br />Number of <b>days</b> since "+dString+": "+DateDiff.inDays(d1, d2));
document.write("<br />Number of <b>weeks</b> since "+dString+": "+DateDiff.inWeeks(d1, d2));
document.write("<br />Number of <b>months</b> since "+dString+": "+DateDiff.inMonths(d1, d2));
document.write("<br />Number of <b>years</b> since "+dString+": "+DateDiff.inYears(d1, d2));

代码样本从这里。