Date Comparison in JavaScript

Comparing Date values

To check the equality of Date values:

var date1 = new Date();
var date2 = new Date(date1.valueOf() + 10);
console.log(date1.valueOf() === date2.valueOf());

Sample output: false

Note that you must use valueOf() or getTime() to compare the values of Date objects because the equality operator will compare if two object references are the same. For example:

var date1 = new Date();
var date2 = new Date();
console.log(date1 === date2);

Sample output: false

Whereas if the variables point to the same object:

var date1 = new Date();
var date2 = date1;
console.log(date1 === date2);

Sample output: true

However, the other comparison operators will work as usual and you can use < and > to compare that one date is earlier or later than the other. For example:

var date1 = new Date();
var date2 = new Date(date1.valueOf() + 10);
console.log(date1 < date2);

Sample output: true

It works even if the operator includes equality:

var date1 = new Date();
var date2 = new Date(date1.valueOf());
console.log(date1 <= date2);

Sample output: true

Date Difference Calculation

To compare the difference of two dates, we can do the comparison based on the timestamp.

var date1 = new Date();
var date2 = new Date(date1.valueOf() + 5000);

var dateDiff = date1.valueOf() - date2.valueOf();
var dateDiffInYears = dateDiff / 1000 / 60 / 60 / 24 / 365; //convert milliseconds into years

console.log("Date difference in years : " + dateDiffInYears);