Unix Timestamp Converter
Convert Unix timestamps to human-readable dates and back. Handles seconds, milliseconds, ISO 8601 and relative time. Timezone-aware.
What is a Unix timestamp?
A Unix timestamp is the number of seconds since 00:00:00 UTC on 1 January 1970 — the moment commonly called the Unix epoch. It is a single integer, which makes it trivial to store, compare and sort.
Seconds vs milliseconds
This is the most common source of confusion:
- 10 digits (e.g.
1736899200) — seconds - 13 digits (e.g.
1736899200000) — milliseconds
JavaScript's Date.now() returns milliseconds, while Math.floor(Date.now() / 1000) returns seconds. This tool detects the difference automatically from the digit count.
Common formats
| Format | Example |
|---|---|
| Unix seconds | 1736899200 |
| Unix milliseconds | 1736899200000 |
| ISO 8601 | 2025-01-15T10:30:00Z |
| RFC 2822 | Wed, 15 Jan 2025 10:30:00 GMT |
| SQL datetime | 2025-01-15 10:30:00 |
The 2038 problem
The Unix epoch is near its upper limit for 32-bit signed integers: 19 January 2038. Systems storing timestamps as 32-bit integers will overflow around then. If you maintain software that will still be running, use 64-bit integers or ISO 8601 strings.
Timezone notes
Unix timestamps are always UTC. The tool shows both the UTC value and your browser's local time so you can confirm the conversion. Daylight saving shifts are handled automatically by your local timezone.
Frequently asked questions
What is a Unix timestamp?
The number of seconds since 00:00:00 UTC on 1 January 1970. It is a single integer, which makes it easy to store, compare and sort.
Is it seconds or milliseconds?
The tool works it out from the digit count. Ten digits is seconds, thirteen digits is milliseconds.
What timezone does it use?
The timestamp itself is always UTC. The output shows both the UTC value and your browser's local time so you can confirm the conversion.
What is the 2038 problem?
Unix timestamps stored as 32-bit signed integers overflow on 19 January 2038. Use 64-bit integers or ISO 8601 strings for anything long-lived.
Can I convert an ISO date string?
Yes. Paste an ISO 8601 string such as 2026-01-15T10:30:00Z and it will convert to a Unix timestamp and every other common format.