JavaScript getTime()

getTime() returns the timestamp stored by a JavaScript Date: milliseconds since 1 January 1970 00:00:00 UTC. Dates before the epoch return negative values.

const date = new Date();
const milliseconds = date.getTime();
console.log(milliseconds);

Timestamps are useful for comparing dates, measuring elapsed time, copying Date objects, and storing an instant independently of display format.

getTime() Syntax Top ↑

const timestamp = date.getTime();

Unix Epoch and Negative Timestamps Top ↑

const epoch = new Date(0);
const beforeEpoch = new Date(-1000);

Compare and Sort Dates Top ↑

const a = new Date("2026-09-10T10:00:00Z");
const b = new Date("2026-09-11T10:00:00Z");
console.log(a.getTime() < b.getTime());

const dates = [b, a];
dates.sort((x, y) => x.getTime() - y.getTime());

Calculate Elapsed Time Top ↑

const start = new Date("2026-09-10T10:00:00Z");
const end = new Date("2026-09-10T10:02:30Z");
const seconds = (end.getTime() - start.getTime()) / 1000;
console.log(seconds); // 150

The original tutorial also uses timestamps to calculate process duration; see the process-time demo.

Copy a Date Object Top ↑

const original = new Date();
const copy = new Date(original.getTime());

getTime() vs Date.now() Top ↑

const fromObject = (new Date()).getTime();
const directly = Date.now();

Use Date.now() when you only need the current timestamp and do not need a Date object.

Invalid Dates and NaN Top ↑

const bad = new Date("invalid");
console.log(bad.getTime()); // NaN

Use the Right API for Performance Timing Top ↑

Date.now() and getTime() represent wall-clock time. For measuring short code execution intervals in a browser, performance.now() provides a monotonic, higher-resolution timer.

const start = performance.now();
// work to measure
const elapsed = performance.now() - start;

Common getTime() Mistakes Top ↑

• Assuming the number is seconds instead of milliseconds.
• Using wall-clock time for precise performance benchmarking.
• Failing to detect NaN for invalid dates.
• Comparing Date objects by identity instead of comparing timestamps.

getMonth() → ← Date Reference

Subhendu Mohapatra

Author & Instructor at plus2net

I write and maintain practical tutorials on Python, PHP, SQL, JavaScript, HTML, jQuery, and web development at plus2net. The tutorials focus on clear explanations, working examples, and code that readers can test and adapt while learning.

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