Date & Timestamp Converter

How it works

Convert between Unix timestamps, ISO 8601 strings, and human-readable dates, view any moment in a chosen timezone, and add or subtract a duration from a date — the day-to-day date math a developer reaches for.

1. Paste a Unix timestamp (seconds or milliseconds), an ISO string, or any date your browser can parse.
2. Or click 'Now' to use the current timestamp.
3. Review the converted formats: Unix (s/ms), ISO 8601, UTC string, local string, relative time, day of week/year, and ISO week number.
4. Use the timezone selector and date math section to view the date elsewhere or shift it by a duration.

Common use cases

• Converting a Unix timestamp from an API response or log line into a readable date.
• Checking what a UTC timestamp corresponds to in a specific timezone before scheduling something.
• Calculating a date N days/months/years from now, e.g. for an expiry or reminder date.
• Looking up the ISO week number or day-of-year for a given date.

FAQ

How does it know if my timestamp is in seconds or milliseconds?

It checks the number of digits: an 11+ digit all-numeric input is treated as milliseconds, shorter numeric input is treated as seconds — matching the typical length difference between the two.

What timezone data does it use?

It relies on the Intl.DateTimeFormat API and IANA timezone database, so results reflect standard timezone rules including daylight saving time where applicable.

Does 'local string' mean my timezone?

Yes — the 'Local String' row reflects your browser/device's configured timezone, while the timezone selector below lets you view the same instant in any other zone.