How to get a timestamp in JavaScript? [Answered]

Short & Snazzy:

+ new Date()

A unary operator like plus triggers the valueOf method in the Date object and it returns the timestamp (without any alteration).

Details:

On almost all current browsers you can use Date.now() to get the UTC timestamp in milliseconds; a notable exception to this is IE8 and earlier (see compatibility table).

You can easily make a shim for this, though:

if (!Date.now) {
    Date.now = function() { return new Date().getTime(); }
}

To get the timestamp in seconds, you can use:

Math.floor(Date.now() / 1000)

Or alternatively, you could use:

Date.now() / 1000 | 0

Which should be slightly faster, but also less readable.

I would recommend using Date.now() (with compatibility shim). It’s slightly better because it’s shorter & doesn’t create a new Date object. However, if you don’t want a shim & maximum compatibility, you could use the “old” method to get the timestamp in milliseconds:

new Date().getTime()

Which you can then convert to seconds like this:

Math.round(new Date().getTime()/1000)

And you can also use the valueOf method which we showed above:

new Date().valueOf()

Timestamp in Milliseconds

var timeStampInMs = window.performance && window.performance.now && window.performance.timing && window.performance.timing.navigationStart ? window.performance.now() + window.performance.timing.navigationStart : Date.now();

console.log(timeStampInMs, Date.now());

Example #2:

I like this, because it is small:

+new Date

I also like this, because it is just as short and is compatible with modern browsers, and over 500 people voted that it is better:

Date.now()

Example #3:

JavaScript works with the number of milliseconds since the epoch whereas most other languages work with the seconds. You could work with milliseconds but as soon as you pass a value to say PHP, the PHP native functions will probably fail. So to be sure I always use the seconds, not milliseconds.

This will give you a Unix timestamp (in seconds):

var unix = Math.round(+new Date()/1000);

This will give you the milliseconds since the epoch (not Unix timestamp):

var milliseconds = new Date().getTime();

Example #4:

var time = Date.now || function() {
  return +new Date;
};

time();

Answer #5:

Quick and dirty solution:

Date.now() /1000 |0

Warning: it might break in 2038 and return negative numbers if you do the |0 magic. Use Math.floor() instead by that time

Math.floor() solution:

Math.floor(Date.now() /1000);

Some nerdy alternative:

new Date/1e3|0

Polyfill to get Date.now() working:

To get it working in IE you could do this (Polyfill from MDN):

if (!Date.now) {
    Date.now = function now() {
        return new Date().getTime();
    };
}

If you do not care about the year / day of week / daylight saving time you need to remember this for dates after 2038:

Bitwise operations will cause usage of 32 Bit Integers instead of 64 Bit Floating Point.

You will need to properly use it as:

Math.floor(Date.now() / 1000)

If you just want to know the relative time from the point of when the code was run through first you could use something like this:

const relativeTime = (() => {
    const start = Date.now();
    return () => Date.now() - start;
})();

In case you are using jQuery you could use $.now() as described in jQuery’s Docs which makes the polyfill obsolete since $.now() internally does the same thing: (new Date).getTime()


Now a tiny explaination of what |0 does:

By providing |, you tell the interpreter to do a binary OR operation.
Bit operations require absolute numbers which turns the decimal result from Date.now() / 1000 into an integer.

During that conversion, decimals are removed, resulting in a similar result to what using Math.floor() would output.

Be warned though: it will convert a 64 bit double to a 32 bit integer.
This will result in information loss when dealing with huge numbers.
Timestamps will break after 2038 due to 32 bit integer overflow unless Javascript moves to 64 Bit Integers in Strict Mode.

How to get timestamp in JavaScript? Answer #6:

Date, a native object in JavaScript is the way we get all data about time.

Just be careful in JavaScript the timestamp depends on the client computer set, so it’s not 100% accurate timestamp. To get the best result, you need to get the timestamp from the server-side.

Anyway, my preferred way is using vanilla. This is a common way of doing it in JavaScript:

Date.now(); //return 1495255666921

In MDN it’s mentioned as below:

The Date.now() method returns the number of milliseconds elapsed since 1 January 1970 00:00:00 UTC.
Because now() is a static method of Date, you always use it as Date.now().

If you using a version below ES5, Date.now(); not works and you need to use:

new Date().getTime();

Answer #7:

Just to add up, here’s a function to return a timestamp string in Javascript. Example: 15:06:38 PM

function displayTime() {
    var str = "";

    var currentTime = new Date()
    var hours = currentTime.getHours()
    var minutes = currentTime.getMinutes()
    var seconds = currentTime.getSeconds()

    if (minutes < 10) {
        minutes = "0" + minutes
    }
    if (seconds < 10) {
        seconds = "0" + seconds
    }
    str += hours + ":" + minutes + ":" + seconds + " ";
    if(hours > 11){
        str += "PM"
    } else {
        str += "AM"
    }
    return str;
}

Answer #8:

Performance

Today – 2020.04.23 I perform tests for chosen solutions. I tested on MacOs High Sierra 10.13.6 on Chrome 81.0, Safari 13.1, Firefox 75.0

Conclusions

  • Solution Date.now() (E) is fastest on Chrome and Safari and second fast on Firefox and this is probably best choice for fast cross-browser solution
  • Solution performance.now() (G), what is surprising, is more than 100x faster than other solutions on Firefox but slowest on Chrome
  • Solutions C,D,F are quite slow on all browsers
enter image description here

Details

Results for Chrome:

enter image description here

Code used in tests is presented in the below snippet:

function A() {
  return new Date().getTime();
}

function B() {
  return new Date().valueOf();
}

function C() {
  return +new Date();
}

function D() {
  return new Date()*1;
}

function E() {
  return Date.now();
}

function F() {
  return Number(new Date());
}

function G() {
  // this solution returns time counted from loading the page.
  // (and on Chrome it gives better precission)
  return performance.now(); 
}



// TEST

log = (n,f) => console.log(`${n} : ${f()}`);

log('A',A);
log('B',B);
log('C',C);
log('D',D);
log('E',E);
log('F',F);
log('G',G);

Hope you learned something from this post.

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