How to get the current timestamp in JavaScript

By Flavio Copes

Learn how to get the current UNIX timestamp in JavaScript with Date.now(), and how to convert it from milliseconds to seconds using Math.floor().

The UNIX timestamp is an integer that represents the number of seconds elapsed since January 1 1970.

On UNIX-like machines, which include Linux and macOS, you can type date +%s in the terminal and get the UNIX timestamp back:

$ date +%s
1524379940

If you have a timestamp and want to know which date it corresponds to (or the reverse), I built a free timestamp converter that handles timezones too.

The current timestamp can be fetched by calling the now() method on the Date object:

Date.now()

You could get the same value by calling

new Date().getTime()

or

new Date().valueOf()

Note: IE8 and below do not have the now() method on Date. Look for a polyfill if you need to support IE8 and below, or use new Date().getTime() if Date.now is undefined (as that’s what a polyfill would do)

The timestamp in JavaScript is expressed in milliseconds.

To get the timestamp expressed in seconds, convert it using:

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

Note: some tutorials use Math.round(), but that will approximate to the next second even if the second is not fully completed.

or, less readable:

~~(Date.now() / 1000)

I’ve seen tutorials using

+new Date

which might seem a weird statement, but it’s perfectly correct JavaScript code. The unary operator + automatically calls the valueOf() method on any object it is assigned to, which returns the timestamp (in milliseconds). The problem with this code is that you instantiate a new Date object that’s immediately discarded.

To generate a date from a timestamp, use new Date(<timestamp>) but make sure you pass a number (a string will get you an “invalid date” result - use parseInt() in doubt)

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