brienblatt.com

Timestamp Converter

The tool I keep reaching for when I'm staring at a log line, a database row, or a JWT and need to know when that actually was. Drop in a Unix epoch — in seconds or milliseconds — or an ISO 8601 string, and get every common format back, plus a relative-time read.

Converter

Detected: date string

ISO 8601 (UTC)
2026-09-09T09:44:05.565Z
Local time
9/9/2026, 5:44:05 AM
Unix (seconds)
1788947045
Unix (milliseconds)
1788947045565
Relative
just now

When this is useful

  • Reading server logs that emit Unix seconds (most syslog-style stacks) or milliseconds (Java, JS, Cloudflare Workers).
  • Decoding JWTs — iat, exp, and nbf are Unix seconds.
  • Database forensics — figuring out exactly when a row was created/modified across timezones.
  • Cron debugging — verifying that "next run" timestamps line up with what you expect locally.
  • API responses that mix unix-ms and ISO strings, especially when one team's "timestamp" disagrees with another's.

Format quick reference

  • Unix seconds — integer, ~10 digits today (e.g. 1705305000). Treat anything under 13 digits as seconds.
  • Unix milliseconds — integer, ~13 digits today (e.g. 1705305000000). What Date.now() returns in JavaScript.
  • ISO 8601 — YYYY-MM-DDTHH:mm:ssZ (e.g. 2024-01-15T08:30:00Z). The trailing Z means UTC; an offset like -05:00 works too.
  • RFC 2822 — Mon, 15 Jan 2024 08:30:00 GMT. Used in HTTP headers, email.

Everything runs locally in your browser via the standard Date object and Intl.RelativeTimeFormat. No request leaves your device.