How do I convert a Unix timestamp to a date?

Enter the value, keep Auto detect unit or select the documented source unit, and choose Convert timestamp. The result shows UTC, browser-local, ISO 8601, and canonical Unix representations.

Is a Unix timestamp in seconds or milliseconds?

The Unix convention is commonly expressed in seconds, while JavaScript Date uses milliseconds. APIs and databases may also use microseconds or nanoseconds, so the source contract is authoritative; auto detection is a convenience heuristic.

How do I convert a date to a Unix timestamp?

Open Date → Unix, enter a date and time, choose whether it should be interpreted as UTC or browser local time, and convert it to seconds and milliseconds.

Is a Unix timestamp always UTC?

A Unix timestamp identifies an instant relative to the UTC epoch and does not store a display timezone. UTC and local output are two representations of the same instant.

Why does JavaScript show the wrong date for a Unix timestamp?

The most common cause is passing Unix seconds to new Date even though it expects milliseconds. Large integers can also lose precision when converted to Number too early.

What is the Year 2038 problem?

Signed 32-bit systems can represent Unix seconds only through 2038-01-19, after which the counter overflows. Modern 64-bit timestamp storage avoids that specific limit, but legacy systems and formats may still be affected.

Does this tool upload my timestamp or date?

No. Conversion, unit detection, comparison, batch processing, exports, and AI-ready context generation run locally in the browser.

Processed locally

Unix Timestamp to Date Online

Convert Unix timestamps to UTC, browser-local, and ISO 8601 dates with automatic seconds, milliseconds, microseconds, and nanoseconds detection.

Overview

What this tool does

Unix Timestamp to Date converts epoch values in seconds, milliseconds, microseconds, or nanoseconds into UTC, browser-local, and ISO 8601 dates. Auto detection is deterministic and can be overridden, while reverse conversion, batch processing, comparison, and precision diagnostics remain available as secondary workflows.

Workflow

How to use

Follow the core workflow below. Use “Show in tool” to locate the real control in the live tool above.

Enter a Unix timestamp
Add a plain integer or fractional value to Unix timestamp. Use Now or Sample only when you need a known starting point.
Unix timestampNowSample
Confirm or change the detected unit
Keep Auto detect unit for an undocumented value, or select Seconds, Milliseconds, Microseconds, or Nanoseconds when the source contract is known.
Auto detect unitSecondsMilliseconds
Compare UTC, local and ISO results
Review Conversion result to compare UTC, Browser local, and ISO 8601 for the same epoch instant, then check the detected unit and timezone labels.
UTCBrowser localISO 8601
Copy the representation you need
Copy the specific display or canonical Unix unit required by your API, log, test, or code path. More canonical units remain available without crowding the primary result.
CopyUnix secondsUnix milliseconds
Enter a date and time
Open Date → Unix and enter the calendar date and time that should be converted into an epoch value. Milliseconds can be included when the source contains them.
Date → UnixDate and time
Choose how to interpret the date
Select UTC when the input already describes universal time, or Browser local time when it should be interpreted using the browser timezone.
Interpret asUTCBrowser local time
Convert the date to Unix time
Run Convert date after confirming the value and timezone interpretation. The conversion produces seconds, milliseconds, and the normalized ISO instant.
Convert date
Review and copy the Unix result
Check the seconds, milliseconds, and ISO 8601 outputs, then copy an individual value or prepare the reverse-conversion context.
SecondsMillisecondsISO 8601Copy
Add timestamps for batch conversion
Open Batch and paste up to 1,000 timestamp values with one value per line. Seconds, milliseconds, microseconds, and nanoseconds can be mixed in the same list.
BatchUnix timestamps
Convert the complete batch
Run Convert batch to process every non-empty line. Invalid values remain visible as errors without preventing valid rows from being converted.
Convert batchClear
Review units, dates, and row status
Inspect the result table to confirm each original value, detected unit, UTC date, ISO 8601 value, and conversion status.
OriginalUnitUTCISO 8601Status
Copy or download the batch result
Copy the complete table, download it as CSV, or prepare summary-only AI-ready context after reviewing the converted rows.
Copy tableDownload CSVPrepare AI-ready context
Enter timestamps A and B
Open Compare and provide the two epoch values whose exact temporal difference you need to measure.
CompareTimestamp ATimestamp B
Confirm the unit of each timestamp
Keep Auto detect when the source units are undocumented, or explicitly select the unit for A and B when their contracts are known.
Unit AUnit BAuto detect
Run the timestamp comparison
Select Compare timestamps after checking both values and units. The tool normalizes both inputs before calculating their exact delta.
Compare timestamps
Review the direction and exact delta
Confirm whether A precedes or follows B, compare their ISO instants, and inspect the delta in seconds, milliseconds, and nanoseconds before preparing context.
A → BDelta secondsDelta millisecondsDelta nanoseconds

Success

You can now convert a timestamp, reverse a date into Unix time, process a batch, compare two instants, and export the representation you need.

Copy a resultDownload CSVPrepare AI-ready context

Practical cases

Examples

Inspect an API or log timestamp

Convert an issued-at, created-at, or event value and compare its UTC and browser-local representations.

Catch the JavaScript seconds pitfall

Check whether a 10-digit value needs to be multiplied by 1,000 before it is passed to the JavaScript Date constructor.

Compare expiry and issued-at

Use Compare to measure the deterministic delta between two timestamps even when their source units differ.

Decode a pre-1970 value

Convert a negative timestamp such as -1 to verify an instant immediately before the Unix epoch.

Troubleshooting

Common errors

Seconds are passed directly to a JavaScript Date constructor that expects milliseconds.
UTC and browser-local displays are treated as different instants instead of different timezone representations.
A large microsecond or nanosecond integer is converted to Number and loses precision.
An out-of-range value is forced into a date instead of checking the source unit.
Changing the timezone label is assumed to change the underlying Unix epoch instant.

From evidence to action

AI workflow

Use Prepare AI-ready context to preview an agent-neutral local export that separates timestamp facts, deterministic diagnostics, and limitations. Single and compare modes include the relevant values and precision warnings; batch mode includes summary counts only. Nothing is sent to an external AI service.

Developer guides

Learn with this tool

Understand the concept, inspect a testable example, then open it in the tool above.

Systems & DevOpsYear 2038 Problem Explained: Unix Time, 32-Bit Overflow, and Y2K38

FAQ

Unix Timestamp to Date Online

What this tool does

How to use

Enter a Unix timestamp

Confirm or change the detected unit

Compare UTC, local and ISO results

Copy the representation you need

Enter a date and time

Choose how to interpret the date

Convert the date to Unix time

Review and copy the Unix result

Add timestamps for batch conversion

Convert the complete batch

Review units, dates, and row status

Copy or download the batch result

Enter timestamps A and B

Confirm the unit of each timestamp

Run the timestamp comparison

Review the direction and exact delta