Date.prototype.getTime()

The getTime() method of {{jsxref("Date")}}  instances returns the number of milliseconds for this date since the epoch, which is defined as the midnight at the beginning of January 1, 1970, UTC.

{{InteractiveExample("JavaScript Demo: Date.prototype.getTime()", "shorter")}} 

const moonLanding = new Date("July 20, 69 20:17:40 GMT+00:00");

// Milliseconds since Jan 1, 1970, 00:00:00.000 GMT
console.log(moonLanding.getTime());
// Expected output: -14182940000

Syntax

getTime()

Parameters

None.

Return value

A number representing the timestamp, in milliseconds, of this date. Returns NaN if the date is invalid.

Description

Date objects are fundamentally represented by a timestamp, and this method allows you to retrieve the timestamp. You can use this method to help assign a date and time to another {{jsxref("Date")}}  object. This method is functionally equivalent to the {{jsxref("Date/valueof", "valueOf()")}}  method.

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 {{jsxref("Date")}}  objects, give the time span between these two calls. This can be used to calculate the executing time of some operations. See also {{jsxref("Date.now()")}}  to prevent instantiating unnecessary {{jsxref("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`);

[!NOTE] In browsers that support the {{domxref("Performance API", "", "", "nocode")}} 's high-resolution time feature, {{domxref("Performance.now()")}}  can provide more reliable and precise measurements of elapsed time than {{jsxref("Date.now()")}} .

Specifications

{{Specifications}} 

Browser compatibility

{{Compat}} 

See also

• {{jsxref("Date.prototype.setTime()")}} 
• {{jsxref("Date.prototype.valueOf()")}} 
• {{jsxref("Date.now()")}}