🕐 Unix Timestamp Converter

Complete Guide: Unix Timestamp Converter

A Unix timestamp (also called epoch time or POSIX time) is the number of seconds elapsed since January 1, 1970, 00:00:00 UTC. It is the foundation of time representation in virtually every programming language, database, operating system, and API. Understanding timestamps — and converting them accurately — is a daily necessity for any developer working with logs, databases, scheduled jobs, or APIs.

Why Unix Timestamps?

Before epoch time became standard, systems used incompatible date formats. A Unix timestamp solves three problems simultaneously: it is timezone-agnostic (always UTC under the hood), arithmetic-friendly (subtract two timestamps to get the duration in seconds), and universally comparable across systems and languages. A timestamp of 1714694400 means exactly the same instant on a Linux server in Berlin, an iOS app in Tokyo, and a PostgreSQL database in São Paulo.

Seconds vs Milliseconds

There are two common Unix timestamp formats:

• Seconds (10 digits) — the standard Unix format, e.g. 1714694400. Used by most Unix/Linux APIs, shell date command, Python's time.time(), and database types like PostgreSQL TIMESTAMPTZ.
• Milliseconds (13 digits) — used by JavaScript's Date.now() and many web APIs. Multiply seconds × 1000 or divide milliseconds ÷ 1000 to convert.

This tool auto-detects which you've entered based on the number of digits. A value greater than 9,999,999,999 is treated as milliseconds.

Code Examples

// JavaScript — current timestamp in seconds
const tsSeconds = Math.floor(Date.now() / 1000);    // 1714694400
const tsMillis  = Date.now();                       // 1714694400000

// JavaScript — timestamp to Date object
const d = new Date(1714694400 * 1000);
console.log(d.toISOString()); // "2024-05-03T00:00:00.000Z"

// JavaScript — date string to timestamp
const ts = Math.floor(new Date('2024-05-03').getTime() / 1000);

// Python — current timestamp
import time
ts = int(time.time())           # seconds since epoch

# Python — timestamp to datetime (UTC)
from datetime import datetime, timezone
dt = datetime.fromtimestamp(1714694400, tz=timezone.utc)
print(dt.isoformat())  # 2024-05-03T00:00:00+00:00

# Python — datetime to timestamp
ts = int(dt.timestamp())

// PHP — current timestamp
$ts = time();                            // seconds
$ts_ms = round(microtime(true) * 1000); // milliseconds

// PHP — timestamp to formatted date
$formatted = date('Y-m-d H:i:s', 1714694400); // "2024-05-03 00:00:00"

// SQL — PostgreSQL
SELECT to_timestamp(1714694400);
SELECT extract(epoch from now())::bigint;

-- MySQL
SELECT FROM_UNIXTIME(1714694400);
SELECT UNIX_TIMESTAMP(NOW());

Timezone Handling

A Unix timestamp always represents an exact UTC moment. The confusion arises when displaying it — the same timestamp shows different clock times in different timezones. When converting for display:

• Store timestamps in UTC in your database. Never store local time.
• Convert to local time only at display time, using the user's browser timezone or an explicit timezone setting.
• Use Intl.DateTimeFormat in JavaScript for correct locale-aware formatting with proper DST handling.

The Year 2038 Problem (Y2K38)

32-bit signed integers overflow at 2147483647 — which corresponds to January 19, 2038, 03:14:07 UTC. Systems storing timestamps in 32-bit integers will wrap around to negative values at that point. Modern 64-bit systems and most databases have already migrated to 64-bit integers, which can represent times billions of years into the future. If you're working with legacy embedded systems, check whether timestamps are stored as int32.

Common Mistakes

• Mixing seconds and milliseconds — the most common bug. Always document your timestamp unit. A date in 2554 usually means someone passed seconds where milliseconds were expected.
• Local time in the database — storing new Date().toString() instead of Date.now() creates timezone-dependent data that breaks when users travel or servers move regions.
• Date comparison without normalization — comparing ISO strings directly as text fails when formats differ (with/without milliseconds, with/without timezone suffix).

For cron scheduling with timestamps, see Cron Visualizer. For generating mock data with timestamps, see Mock JSON Generator.