Unix Timestamp Converter
Convert between a Unix epoch timestamp and a human date and time.
Results update as you type.
About this calculator
A Unix timestamp is the number of seconds since 1 January 1970 UTC (the "epoch"). This converter turns an epoch timestamp into a readable UTC and local date, or takes a date and time and returns its epoch value. It handles both seconds and milliseconds, shows the ISO 8601 form, and names the weekday. A staple for developers reading logs, databases and API responses.
Pick a direction: give it an epoch number and it shows that exact instant both in UTC and in your browser’s local time zone (the two lines differ by your UTC offset), plus the ISO 8601 string and the weekday. Give it a date and a local time instead and it returns the matching epoch value. Because seconds-based timestamps and the millisecond timestamps used by JavaScript differ by a factor of 1,000, a unit switch lets you read or produce either.
For example, the timestamp 1700000000 is Tuesday 14 November 2023 22:13:20 UTC; the ten-digit length is a clue it is in seconds, whereas a thirteen-digit value like 1700000000000 is the same instant in milliseconds. Developers use this to decode a created_at column, sanity-check an API response, set an expiry, or convert a log line’s epoch stamp into a human date.
Frequently asked questions
Is a Unix timestamp in seconds or milliseconds?
The classic Unix timestamp is in seconds since the 1970 epoch, but JavaScript and many APIs use milliseconds (1000× larger). Set the unit under advanced options to read a value either way.
What time zone does the timestamp represent?
A Unix timestamp has no time zone — it is an absolute instant. The tool shows that instant both as UTC and in your browser’s local time, which is why the two lines can differ by your UTC offset.
How can I tell if a timestamp is in seconds or milliseconds?
Count the digits: a present-day seconds timestamp is about 10 digits long, while the millisecond version is about 13 digits. If a decoded date lands near 1970, you probably read a millisecond value as seconds.
What is the Unix epoch?
The epoch is the zero point of Unix time: midnight UTC on 1 January 1970. Every timestamp is just the number of seconds (or milliseconds) counted from that instant.
Can it convert a date back into a timestamp?
Yes. Switch the direction to Date → timestamp, enter the date and local time, and it returns the epoch value, so you can round-trip in either direction.
What is the year 2038 problem?
Systems that store Unix time in a signed 32-bit integer overflow on 19 January 2038, after which the count can no longer increase. Modern 64-bit timestamps avoid this, and this converter handles dates well beyond 2038.
API — use this calculator from code
Call this calculator as a free JSON endpoint — no key required. Send the field values below as query parameters or JSON. Read the full API docs →
Endpoint
GET https://calculator.free/api/v1/unix-timestamp/curl
curl "https://calculator.free/api/v1/unix-timestamp/?mode=to_date&unix=1700000000"JavaScript fetch()
const r = await fetch(
"https://calculator.free/api/v1/unix-timestamp/?" + new URLSearchParams({
"mode": "to_date",
"unix": "1700000000"
}));
const data = await r.json();
console.log(data.results);Results are estimates for general guidance only, not financial, medical or tax advice.