JavaScript Date getTime() Method

What You’ll Learn

getTime() returns the number of milliseconds since the Unix epoch (Jan 1, 1970 UTC) for a Date instant. This guide covers syntax, duration math, timestamp round-trips, comparisons, and how it differs from getMilliseconds().

Introduction

APIs, databases, and sort functions often store time as a single number. The getTime() method exposes that number from any Date object—milliseconds elapsed since January 1, 1970 00:00:00 UTC.

Use it for elapsed duration, ordering events, and serializing instants. For the current timestamp without building a Date, see Date.now().

Understanding the getTime() Method

Date.prototype.getTime() is a zero-argument instance method. It never mutates the original Date—it returns the stored instant as a numeric timestamp.

The same instant always yields the same getTime() value regardless of local timezone. That makes it ideal for comparison and arithmetic; local getters like getHours() are for display, not for measuring duration.

📝 Syntax

dateObj.getTime()

Parameters

• None.

Return value

• Number of milliseconds since the Unix epoch for a valid Date.
• NaN if dateObj is an invalid Date.

Examples Gallery

Open DevTools Console (F12) or use Try-it links. Sample timestamps will differ on your machine when reading “now.”

const now = new Date();
const timestamp = now.getTime();

console.log("Timestamp (ms):", timestamp);

Timestamp (ms): 1721203200123

const start = new Date(2026, 0, 1);
const end = new Date(2026, 1, 1);

const diffMs = end.getTime() - start.getTime();
const diffDays = diffMs / (1000 * 60 * 60 * 24);

console.log("Difference (ms):", diffMs);
console.log("Difference (days):", diffDays);

Difference (ms): 2678400000
Difference (days): 31

const timestamp = 1721203200000;
const restored = new Date(timestamp);

console.log(restored.toISOString());
// 2024-07-17T08:00:00.000Z

2024-07-17T08:00:00.000Z

const meetingA = new Date(2026, 6, 4, 10, 0);
const meetingB = new Date(2026, 6, 4, 14, 30);

if (meetingA.getTime() < meetingB.getTime()) {
  console.log("Meeting A is earlier.");
} else {
  console.log("Meeting B is earlier or same.");
}

Meeting A is earlier.

const start = Date.now();

let sum = 0;
for (let i = 0; i < 200000; i++) {
  sum += i;
}

const elapsed = Date.now() - start;
console.log("Elapsed:", elapsed, "ms");

Elapsed: 3 ms

🚀 Common Use Cases

• API payloads — store createdAt as epoch ms.
• Sorting events — order by getTime().
• Cooldown timers — compare now vs last action timestamp.
• Session expiry — Date.now() > expiresAt.
• Benchmarks — measure code block duration.
• Cache keys — bust caches with timestamp suffixes.

📝 Notes

• getTime() equals valueOf() on valid dates.
• Invalid dates return NaN—use that for validation.
• Not the same as getMilliseconds() (0–999 sub-second).
• Prefer Date.now() when you only need the current ms once.
• Divide carefully when converting ms to days (watch DST if using local midnight tricks).
• For high-precision benchmarks in browsers, consider performance.now() (relative, not epoch).

💡 Best Practices