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Date Converter

Convert Unix timestamps in seconds or milliseconds to ISO 8601, RFC 5322, UTC, local or custom-formatted dates and back, live in your browser.

Your inputs and files stay in your browser

Enter a Unix timestamp (seconds or milliseconds) or an ISO 8601 date.

The converted date appears here.

Same instant

On this page

Turn a Unix timestamp into a readable date or a date string back into a timestamp. The converter recognises seconds, milliseconds and ISO 8601 automatically and outputs ISO, RFC 5322, UTC, your local time, a European format or your own pattern.

Detailed Functionality

In auto-detect mode a plain number with up to 11 integer digits is read as Unix seconds and a longer one as milliseconds; negative values (dates before 1970) and fractions are accepted. Anything else is parsed as a date string: ISO 8601 (2024-02-29T12:00:00Z), RFC 5322 (Tue, 14 Nov 2023 22:13:20 GMT) and other formats your browser's date parser understands. You can also force the input type to seconds, milliseconds or ISO 8601 — then hex or exponent notation such as 0x10 or 1e3 is rejected instead of being guessed.

Eight output formats are available: ISO 8601 in UTC with milliseconds, European dd.MM.yyyy HH:mm:ss, the UTC string, a local string written in the page language with your time zone, RFC 2822/5322 with a numeric +0000 zone, Unix seconds, Unix milliseconds and a custom pattern built from yyyy, MM, dd, HH, mm, ss and SSS. The result updates as you type, and Current Time (Now) fills in the current moment.

Everything runs in JavaScript with the browser's own Date and Intl APIs; the values you paste are not sent anywhere. The supported range is that of JavaScript dates — about ±273,000 years around 1970; values outside it are reported as invalid.

Practical Examples

Timestamp from a log: 1700000000 (seconds) → ISO 8601 2023-11-14T22:13:20.000Z. The same moment in milliseconds, 1700000000000, is detected automatically.

Date to Unix time: 2024-02-29T12:00:00Z with the Unix Timestamp (Seconds) output gives 1709208000.

Before the epoch: -86400 → 1969-12-31T00:00:00.000Z, exactly one day before 1 January 1970.

Email header date: 1700000000 with the RFC 2822 / 5322 output gives Tue, 14 Nov 2023 22:13:20 +0000.

How to Use This Tool

  1. Paste a value

    Enter a Unix timestamp or a date string into Date / Timestamp input, or press Current Time (Now) to insert the current time.

  2. Check the input type

    Leave Input Type on Auto-detect or pick seconds, milliseconds or ISO 8601 explicitly when the value is ambiguous.

  3. Choose the output

    Select a format in Output Format; for Custom Format, type a pattern such as yyyy-MM-dd HH:mm.

  4. Copy the result

    The result updates automatically (Convert recalculates on demand); press Copy to copy it.

Tips and Best Practices

  • Milliseconds from before March 1973 have 11 digits or fewer and would be read as seconds in auto mode — select the milliseconds input type for them.
  • An ISO string without a time zone (2024-02-29T12:00) is interpreted in your local time zone; add Z or an offset such as +03:00 for UTC-safe input.
  • ISO 8601, UTC and RFC outputs are always in UTC; European and custom formats use your browser's local time zone.
  • In custom patterns MM is the month and mm the minutes; all other characters are copied literally.
  • The local string follows the page language, so the same moment reads differently on the English and the Russian page.