Date.prototype.getTime()
The getTime()
method returns the number of milliseconds since the epoch, which is defined as the midnight at the beginning of January 1, 1970, UTC.
You can use this method to help assign a date and time to another Date
object. This method is functionally equivalent to the valueOf()
method.
Try it
Syntax
getTime()
Return value
A number representing the milliseconds elapsed between 1 January 1970 00:00:00 UTC and the given date.
Description
To offer protection against timing attacks and fingerprinting, the precision of
new Date().getTime()
might get rounded depending on browser settings. In
Firefox, the privacy.reduceTimerPrecision
preference is enabled by default
and defaults to 20µs in Firefox 59; in 60 it will be 2ms.
// reduced time precision (2ms) in Firefox 60
new Date().getTime();
// 1519211809934
// 1519211810362
// 1519211811670
// …
// reduced time precision with `privacy.resistFingerprinting` enabled
new Date().getTime();
// 1519129853500
// 1519129858900
// 1519129864400
// …
In Firefox, you can also enable privacy.resistFingerprinting
, the
precision will be 100ms or the value of
privacy.resistFingerprinting.reduceTimerPrecision.microseconds
, whichever
is larger.
Examples
Using getTime()
for copying dates
Constructing a date object with the identical time value.
// Since month is zero based, birthday will be January 10, 1995
const birthday = new Date(1994, 12, 10);
const copy = new Date();
copy.setTime(birthday.getTime());
Measuring execution time
Subtracting two subsequent getTime()
calls on newly generated
Date
objects, give the time span between these two calls. This can be used
to calculate the executing time of some operations. See also Date.now()
to
prevent instantiating unnecessary Date
objects.
let end, start;
start = new Date();
for (let i = 0; i < 1000; i++) {
Math.sqrt(i);
}
end = new Date();
console.log(`Operation took ${end.getTime() - start.getTime()} msec`);
Specifications
Specification |
---|
ECMAScript Language Specification # sec-date.prototype.gettime |
Browser compatibility
BCD tables only load in the browser