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Tool 5.12

Unix timestamp converter (epoch to date and back)

Convert Unix timestamps in seconds or milliseconds to ISO 8601, UTC and your local time, or a date back to epoch. Detects the unit and shows relative time.

Runs on your deviceRuns entirely in your browser: nothing you type or upload leaves your device.

How to use it

  1. Paste a Unix timestamp (seconds, ms, µs or ns) or a date like 2025-01-31T14:30:00Z.
  2. The unit is detected automatically; change it if needed.
  3. Copy the format you need: Unix seconds or milliseconds, ISO 8601, UTC or local time.

Where you find these long numbers

Databases, server logs, APIs, exported spreadsheets and app records often store time as a plain number like 1735689600: the seconds since 1 January 1970 in UTC. It is easy for computers to compare and it means the same moment everywhere, but nobody can read it at a glance.

Paste the number and the tool shows it as a readable date in UTC and in your own time zone, how long ago it was, and the same moment in the other common formats. It also works the other way: type a date and get its Unix time. The conversion runs in your browser.

Example: the New Year that happened on 31 December

Paste 1735689600. The tool reads it as seconds (10 digits) and shows 2025-01-01T00:00:00.000Z in the ISO 8601 (UTC) row: midnight, New Year's Day. In Colombia, UTC−5 all year, the ISO 8601 (your time zone) row shows 2024-12-31T19:00:00.000-05:00: 7 p.m. on 31 December.

That five-hour gap explains many report problems. A payment stored at that timestamp belongs to December for a customer in Bogotá but to January for a report that groups by UTC dates. When two systems disagree about the day of a transaction, check which time zone each one uses. The same number with 13 digits, 1735689600000, is read as milliseconds and gives the same date.

Typing dates: use year-month-day

Don't type dates as dd/mm/aaaa. Browsers read slashed dates the US way, month first, so 05/03/2025 becomes 3 May, not 5 March, and 31/01/2025 is usually rejected as invalid. Type 2025-03-05 (year-month-day) and there is no ambiguity.

One more trap: a date alone, like 2025-03-05, is read as midnight UTC, which in Colombia is 7 p.m. the day before. If you mean midnight in your own time zone, add the time: 2025-03-05T00:00. A date and time without Z or an offset is always read as your local time.

FAQ

How do I get the current Unix time?

It is at the top of this page, under Current Unix time, and the Now button copies it into the converter. In a terminal on Linux or macOS, `date +%s` prints it in seconds; in PowerShell, `[DateTimeOffset]::UtcNow.ToUnixTimeSeconds()`. In JavaScript, `Date.now()` gives milliseconds, so divide by 1000 for seconds.

How do I know if it's seconds or milliseconds?

Current timestamps have 10 digits in seconds and 13 in milliseconds. The tool detects the unit by size, and you can force it.

What about the year 2038 problem?

Systems that store Unix time as a signed 32-bit number overflow on January 19, 2038. This converter has no 32-bit limit and handles dates far beyond that.

How do I convert a Unix timestamp in Excel?

Excel counts days since 1900, not seconds since 1970. With the timestamp in A1, use `=A1/86400+25569` and format the cell as a date: that gives UTC. For Colombia's time, subtract 5 hours: `=A1/86400+25569-5/24`. If the timestamp has 13 digits, divide by 86400000 instead.

Why is my date one day off?

You probably entered a date without a time, which is read as midnight UTC. In the Americas that moment is still the previous evening, so the local row shows the day before. Add a time, like `2025-03-05T00:00`, to mean midnight where you are.

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