What is a Unix epoch timestamp?

A Unix epoch timestamp counts time from January 1, 1970 at 00:00:00 UTC. Many logs, databases, APIs, and scripts use epoch seconds or milliseconds.

Are epoch seconds and milliseconds different?

Yes. Epoch seconds count whole seconds since the Unix epoch. Epoch milliseconds count thousandths of a second and are common in JavaScript and web APIs.

Why do local time and UTC look different?

UTC is a global time standard. Local time applies your computer's time zone offset and daylight saving rules, so the displayed clock time may differ.

Free developer time converter

Unix Epoch Timestamp Converter

Convert Unix epoch seconds or milliseconds into local time, UTC, ISO format, and convert a chosen date and time back into epoch timestamps.

Epoch seconds
Milliseconds
UTC and local
ISO timestamps

Readable result

Epoch breakdown

Epoch seconds0

Local time: -
UTC time: -
ISO timestamp: -
Relative to now: -

Reverse converter

Convert date and time to epoch

Choose a local date and time to generate Unix epoch seconds, epoch milliseconds, and UTC output for scripts, logs, and API testing.

Local date and time

Epoch seconds: -
Epoch milliseconds: -
UTC time: -
Local time: -

How Unix epoch timestamps work

A Unix epoch timestamp counts time from January 1, 1970 at 00:00:00 UTC. System logs, databases, APIs, cloud dashboards, authentication events, and scheduled jobs often use epoch values because they are compact and timezone-neutral.

Epoch seconds are common in Linux and server logs. Epoch milliseconds are common in JavaScript because the browser `Date` object stores time internally in milliseconds.

Seconds vs milliseconds

If a timestamp looks like ten digits, it is probably epoch seconds. If it looks like thirteen digits, it is probably epoch milliseconds. Choosing the wrong unit can shift the displayed date wildly, which is one of the most common timestamp debugging mistakes.

This converter lets you choose the unit explicitly so you can check both interpretations while debugging.

Timestamp shape	Likely unit	Common source
10 digits	Seconds	Linux logs, APIs, database fields
13 digits	Milliseconds	JavaScript, browser events, web APIs
16 digits	Microseconds	Some databases and tracing systems
19 digits	Nanoseconds	High-resolution logs and telemetry

UTC, local time, and ISO format

The timestamp itself does not store your time zone. UTC output is useful when comparing server logs across systems. Local output is useful when matching an event to what a person saw on their clock.

ISO timestamps are especially useful in APIs and documentation because they include a predictable date and time format. A trailing `Z` means the ISO timestamp is expressed in UTC.

For example, an event that happened at 18:00 UTC may appear as afternoon or evening local time depending on the viewer's time zone. When teams compare logs across regions, UTC should be the shared reference.

Common timestamp mistakes

Common mistakes include mixing seconds and milliseconds, comparing UTC server logs to local screenshots without applying the time zone difference, and assuming daylight saving time rules were the same for every date. When troubleshooting, keep the original timestamp, UTC time, and local time together.

Timestamp debugging checklist

When a timestamp looks wrong, first confirm whether the value is in seconds or milliseconds. Then compare the UTC output with the local output, check whether daylight saving time applied on that date, and verify whether the system that produced the timestamp used UTC or a local clock.

If an API response, database row, and application log disagree, record all three forms together: the original numeric timestamp, the ISO UTC timestamp, and the local display time. That makes it much easier to spot unit and timezone mismatches.