<p>I want a single number that represents the current date and time, like a <a href="https://en.wikipedia.org/wiki/Unix_time" rel="noreferrer">Unix timestamp</a>.</p>

Timestamp in milliseconds
To get the number of milliseconds since
Unix epoch
, call
```
Date.now
```
:
```
```
Date.now()
```
```
Alternatively, use the unary operator
```
+
```
to call
```
Date.prototype.valueOf
```
:
```
```
+ new Date()
```
```
Alternatively, call
```
valueOf
```
directly:
```
```
new Date().valueOf()
```
```
To support IE8 and earlier (see
compatibility table
), create a
shim
for
```
Date.now
```
:
```
```
if (!Date.now) {
    Date.now = function() { return new Date().getTime(); }
}
```
```
Alternatively, call
```
getTime
```
directly:
```
```
new Date().getTime()
```
```
Timestamp in seconds
To get the number of seconds since
Unix epoch
, i.e.
Unix timestamp
:
```
```
Math.floor(Date.now() / 1000)
```
```
Alternatively, using bitwise-or to floor is slightly faster, but also less readable and may break in the future (see explanations
1
,
2
):
```
```
Date.now() / 1000 | 0
```
```
Timestamp in milliseconds (higher resolution)
Use
```
performance.now
```
:
```
```
var isPerformanceSupported = (
    window.performance &&
    window.performance.now &&
    window.performance.timing &&
    window.performance.timing.navigationStart
);

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

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