What Is a Unix Timestamp?

A Unix timestamp (also called epoch time or POSIX time) is the number of seconds that have elapsed since January 1, 1970, 00:00:00 UTC — called the Unix Epoch. It is timezone-independent: the same timestamp represents the exact same moment anywhere in the world. For example, timestamp 0 is 1970-01-01T00:00:00Z, and 1700000000 is November 14, 2023 22:13:20 UTC.

Seconds vs Milliseconds — Auto-Detection

Unix timestamps are commonly stored in two precisions:

• Seconds — Standard POSIX time. Current value (2026): around 1,744,000,000.
• Milliseconds — Used in JavaScript (Date.now()), Java (System.currentTimeMillis()), and most web APIs. Current value: around 1,744,000,000,000.

This tool auto-detects which precision you entered: values above 10,000,000,000 are treated as milliseconds; smaller values as seconds. A badge next to the input field shows which was detected.

Output Formats Explained

• Local — The date and time in the timezone you selected, formatted for readability.
• UTC — The date in Coordinated Universal Time (same as GMT+0). Timezone-neutral.
• ISO 8601 — Machine-readable standard format: 2024-11-15T00:00:00.000Z. Used in JSON APIs, databases, and HTML date inputs.
• RFC 2822 — Email and HTTP header format: Thu, 15 Nov 2024 00:00:00 +0000. Used in SMTP, HTTP Date headers, and email clients.
• Relative — Human-readable description: "3 days ago", "in 2 hours". Computed from the current time.

How to Convert a Timestamp — Step by Step

1. Paste your Unix timestamp into the Unix Timestamp input field (or click Use (seconds) / Use (ms) to use the current time).
2. The unit badge will show sec or ms — verify it matches your expected precision.
3. Select your Timezone to see the local representation.
4. The right panel shows all output formats simultaneously — click Copy next to the one you need.
5. To convert a date back to a timestamp, click Date → Timestamp and use the datetime picker.

Common Use Cases

• API debugging — REST APIs often return created_at or expires_at as epoch seconds or milliseconds. Paste the value here to see the human-readable date.
• Database timestamps — MySQL, PostgreSQL, and SQLite store timestamps as integers. Convert to verify data correctness.
• JWT expiry — JSON Web Tokens include exp (expiry) and iat (issued at) as Unix seconds. Use this tool to check if a token has expired.
• Log analysis — Server logs often use epoch seconds. Convert to correlate with events in a specific timezone.
• Scheduling — Calculate future timestamps (e.g. "what epoch second is midnight next Monday UTC?") using the Date → Timestamp direction.

The Year 2038 Problem

Many older systems store Unix timestamps as a 32-bit signed integer. The maximum value of a signed 32-bit integer is 2,147,483,647 — which corresponds to January 19, 2038, 03:14:07 UTC. After this moment, 32-bit systems will overflow and typically roll back to 1901 or produce incorrect dates. This is known as the Year 2038 Problem (analogous to the Y2K bug). Modern systems use 64-bit integers, which can represent dates billions of years into the future.

Time Unit Reference

Related Tools

• Date Difference Calculator — calculate the exact difference between two dates.
• JWT Decoder — decode JWTs and inspect exp / iat claims as timestamps.
• Hash Generator — generate cryptographic hashes.
• Number Base Converter — convert timestamps between decimal, hex, and binary.