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Unix Timestamp Converter

Convert Unix epoch seconds or ms to UTC and local dates, and dates back to timestamps. Free online tool — no sign-up. Runs locally in your browser.

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How to use

Follow these steps for a clear answer.

1

Enter a timestamp or date

Paste epoch seconds/ms, or type an ISO date to convert the other way.

2

Convert

Read UTC ISO, local time, and both second and millisecond epochs.

3

Copy values

Use Copy on the fields you need for APIs, logs, or JWT claims.

Unix timestamp converter specification

Version 1.0.0 · Last reviewed 2026-07-29

Definition
A Unix timestamp counts seconds (or milliseconds) since the Unix epoch: 1970-01-01T00:00:00Z.
What it calculates
Unix epoch seconds/milliseconds ↔ ISO-8601 UTC and local calendar fields.
Inputs
  • Epoch number (seconds or milliseconds)
  • Or an ISO-8601 / parseable date-time string
Outputs
  • Seconds and milliseconds since epoch
  • UTC ISO-8601 string
Formula
ms = s × 1000; Date = new Date(ms); s = floor(ms / 1000)

Convert Unix timestamps (epoch seconds or milliseconds) to readable dates, and convert dates back to epoch values. Useful for APIs, logs, JWT exp/iat, and database fields.

Quick examples

Epoch Unit UTC
0 seconds 1970-01-01T00:00:00.000Z
1700000000 seconds 2023-11-14T22:13:20.000Z
1700000000000 milliseconds same instant as above

Seconds vs milliseconds

  • Seconds — classic Unix / Linux date +%s, many databases, JWT claims.
  • Milliseconds — JavaScript Date.now(), many JSON APIs.

If the absolute value is below 1e12, this tool treats the input as seconds unless you force milliseconds.

Assumptions
  • Auto unit: |n| < 1e12 → seconds, else milliseconds (override available in UI).
  • Runs locally in the browser.
Units
  • s: Unix seconds
  • ms: Unix milliseconds
Boundary conditions
  • Invalid numbers or unparseable dates yield an error state.
  • Very large magnitudes may exceed JavaScript Date range.
Example
0 → 1970-01-01T00:00:00.000Z; 1700000000 → 2023-11-14T22:13:20.000Z
Validation cases
  • 0 seconds → ISO → 1970-01-01T00:00:00.000Z
  • 1700000000 seconds → ISO → 2023-11-14T22:13:20.000Z
  • 1700000000000 ms → seconds → 1700000000
Sources
  • POSIX / Unix epoch
  • ECMAScript Date (milliseconds since epoch)
Last reviewed
2026-07-29
Calculation version
1.0.0
→ Crontab Generator › → Base64 Decoder & Encoder › → Today's Date ›

Frequently asked questions

Key distinctions behind the tool.

Seconds or milliseconds?

Classic Unix time is seconds since 1970-01-01 UTC. Many APIs use milliseconds. This tool auto-detects: values with absolute magnitude under 1e12 are treated as seconds.

What timezone is shown?

UTC is always shown as ISO-8601. Local time uses your browser timezone.

Does it upload my timestamps?

No. Conversion runs entirely in your browser.