Timestamp Converter

What is a Unix timestamp

A Unix timestamp is simply the number of seconds that have elapsed since 00:00:00 UTC on 1 January 1970 — an arbitrary but universally-agreed zero point known as the Unix epoch. It is the native time representation inside databases, logs, APIs, and most programming languages because it is unambiguous, timezone-free, and easy to arithmetic on.

Seconds vs milliseconds

The original Unix timestamp is in seconds. JavaScript's Date.now() and most modern web APIs use milliseconds (1000x larger). This converter auto-detects which you mean based on the number of digits: 10 digits → seconds, 13 digits → milliseconds. A timestamp in seconds for today will be around 1,700,000,000; in milliseconds, around 1,700,000,000,000.

Common formats you get back

• ISO 8601 (2026-04-22T12:34:56.000Z) — the canonical machine-readable format. Use this in APIs and logs.
• UTC string (Wed, 22 Apr 2026 12:34:56 GMT) — verbose but immediately readable.
• Local time — the same instant, expressed in your browser's timezone.
• Relative (3 hours ago) — useful for quickly estimating how old something is.

The Year 2038 problem

Systems storing Unix timestamps as signed 32-bit integers will overflow on 19 January 2038, wrapping back to 1901. Modern systems use 64-bit integers and are safe for roughly 292 billion years. If you maintain legacy C code, check your integer widths.