JavaScript Timestamp Converter
Convert Unix timestamps into readable dates and convert dates back into timestamps with this free JavaScript timestamp converter. Understand Unix seconds, JavaScript milliseconds, ISO 8601 dates, UTC, and local time without performing manual calculations.
Whether you're debugging an API response, inspecting JWT expiration claims, analyzing server logs, or working with JavaScript Date objects, understanding timestamps helps you identify exactly when an event occurred.
Seconds or milliseconds? Unix timestamps commonly use seconds, while JavaScript's Date.now() returns milliseconds. Check the unit before converting a value to avoid dates far in the past or future.
What Is a Unix Timestamp?
A Unix timestamp, also called epoch time, represents the number of seconds elapsed since January 1, 1970, at 00:00:00 UTC. This starting point is known as the Unix epoch.
Unlike a formatted date such as October 9, 2025, a Unix timestamp stores a numeric value representing a specific moment in time. Applications can convert that value into a readable date for different time zones.
Example timestamp
ISO 8601 result: 2025-10-09T08:53:20.000Z
The trailing Z indicates that the displayed date and time use UTC.
Timestamp to Date Conversion
Converting a timestamp into a readable date makes numeric values from APIs, databases, and logs easier to understand. In JavaScript, the Date constructor expects milliseconds, so Unix timestamps expressed in seconds must be multiplied by 1,000 first.
How to convert a timestamp
1
Copy your timestamp.Find the numeric value in your API response, log entry, database record, or application output.
2
Identify the unit.Determine whether the value represents seconds or milliseconds since the Unix epoch.
3
Convert it to a date.Use the appropriate JavaScript conversion and inspect the resulting date in UTC or your local time zone.
const timestampInSeconds = 1760000000;
const date = new Date(timestampInSeconds * 1000);
console.log(date.toISOString());
// 2025-10-09T08:53:20.000Z
For a timestamp already expressed in milliseconds, pass it directly to new Date() without multiplying it by 1,000.
Date to Timestamp Conversion
You can also convert a date and time into Unix seconds or JavaScript milliseconds. This is useful when preparing API payloads, storing dates in databases, comparing event times, or testing scheduled tasks.
Conversion example
Input date: January 1, 2026, at 00:00:00 UTC
| Output format | Result |
|---|
| Unix seconds | 1767225600 |
| Unix milliseconds | 1767225600000 |
| ISO 8601 UTC | 2026-01-01T00:00:00.000Z |
Convert a JavaScript Date into seconds
const date = new Date("2026-01-01T00:00:00.000Z");
const seconds = Math.floor(date.getTime() / 1000);
const milliseconds = date.getTime();
console.log(seconds); // 1767225600
console.log(milliseconds); // 1767225600000
Important: Specify the intended time zone when entering a date. A date without an explicit time zone can be interpreted differently depending on its format and the JavaScript environment.
Unix Seconds vs. JavaScript Milliseconds
Seconds and milliseconds represent elapsed time using different units. Confusing the two is a common cause of incorrect dates in JavaScript applications.
| Comparison | Unix seconds | Milliseconds |
|---|
| Unit | Seconds | Milliseconds |
| Typical current value | About 10 digits | About 13 digits |
| Example | 1760000000 | 1760000000000 |
| JavaScript conversion | new Date(ts * 1000) | new Date(ts) |
| Common source | Unix tools and some APIs | Date.now() |
For a straightforward conversion, multiply seconds by 1,000 to obtain milliseconds. Divide milliseconds by 1,000 to obtain seconds. Use Math.floor() when you need a whole-second timestamp.
Digit length is only a guideline. Ten-digit values often represent seconds and thirteen-digit values often represent milliseconds for modern dates. Older dates, future dates, and custom timestamp formats may not follow this pattern.
JavaScript Timestamp Conversion Examples
JavaScript provides built-in methods for creating timestamps, converting them to dates, and producing standardized date strings. These examples cover common developer tasks.
1. Get the current timestamp in milliseconds
const milliseconds = Date.now();
console.log(milliseconds);
Date.now() returns the number of milliseconds elapsed since the Unix epoch.
2. Get the current Unix timestamp in seconds
const seconds = Math.floor(Date.now() / 1000);
console.log(seconds);
This format is useful when an API or backend system expects Unix seconds instead of JavaScript milliseconds.
3. Convert seconds to a readable date
const timestamp = 1760000000;
const date = new Date(timestamp * 1000);
console.log(date.toISOString());
4. Convert milliseconds to a readable date
const timestamp = 1760000000000;
const date = new Date(timestamp);
console.log(date.toISOString());
5. Convert a date to ISO 8601
const now = new Date();
console.log(now.toISOString());
The toISOString() method returns a standardized date-time string in UTC, typically formatted like 2026-10-15T05:06:10.000Z.
Time Zones and ISO 8601
A Unix timestamp represents one instant in time. Its displayed calendar date and clock time can change depending on the time zone used to format it. For example, the same instant can fall on different calendar dates in UTC and another region.
UTC
Coordinated Universal Time
UTC provides a consistent reference for APIs, server logs, database values, and timestamps shared between systems.
Local time
Your system's time zone
Local formatting displays the same instant using the time zone configured in the environment, which may differ from UTC.
What does ISO 8601 mean?
ISO 8601 is a standard for representing dates and times in a consistent, machine-readable format. A common UTC representation is:
2026-10-15 represents the calendar date.T separates the date and time.05:06:10.000 represents the time, including milliseconds.Z indicates that the time is expressed in UTC.
ISO 8601 strings are especially useful when exchanging date values through JSON APIs, application logs, and backend services.
Common Uses for a JavaScript Timestamp Converter
API debugging
Convert fields such as created_at, updated_at, and expires_at into readable dates when inspecting API responses.
JWT expiration checks
Interpret numeric claims such as exp, iat, and nbf. These claims commonly use Unix seconds.
Server and application logs
Translate numeric timestamps to readable dates to investigate errors, requests, events, and security activity.
Database development
Understand stored epoch values and convert dates into numeric values for testing queries and application logic.
Scheduled jobs
Check expiration dates, reminders, cron schedules, and time-dependent application behavior.
Frontend development
Convert timestamps returned by APIs into dates suitable for displaying in a user's interface.
Privacy When Converting Timestamps
Timestamps can reveal event timing, account activity, or details about internal systems. When working with sensitive logs or API data, consider whether the tool processes values locally or sends them to a remote server.
Good practice: Avoid pasting passwords, access tokens, or complete authentication payloads into tools that do not need them. If you are inspecting a JWT, extract only the timestamp claim you need.
For private or production data, verify the tool's actual processing behavior and privacy policy before using it. Browser-based processing can help reduce unnecessary data transfers when implemented correctly.
JavaScript Timestamp Converter FAQ
What is a JavaScript timestamp converter?
It is a tool for converting Unix epoch timestamps into readable dates and converting dates back into timestamp values. It is particularly useful for working with JavaScript dates, APIs, logs, and databases.
What is the difference between Unix seconds and milliseconds?
Unix seconds count elapsed seconds since January 1, 1970, at 00:00:00 UTC. Milliseconds count elapsed milliseconds from the same starting point. Millisecond values are 1,000 times larger than equivalent second values.
How can I tell whether a timestamp uses seconds or milliseconds?
Modern Unix timestamps in seconds are commonly 10 digits long, while JavaScript millisecond timestamps are commonly 13 digits long. Treat this as a guideline rather than a guarantee, and confirm the expected unit whenever possible.
What does Date.now() return in JavaScript?
Date.now() returns the current time as milliseconds elapsed since the Unix epoch. To get a whole-second timestamp, use Math.floor(Date.now() / 1000).
How do I convert milliseconds to seconds in JavaScript?
Divide the millisecond value by 1,000. Use Math.floor(timestamp / 1000) if you need a whole number of seconds.
const seconds = Math.floor(Date.now() / 1000);
What is ISO 8601 format?
ISO 8601 is a standard date-time representation. A common JavaScript output is 2026-10-15T05:06:10.000Z, where the trailing Z indicates UTC.
Does a Unix timestamp contain a time zone?
No. A Unix timestamp identifies an instant in time rather than a local time zone. You can display that instant in UTC or format it using a specified time zone.
Why does my converted date show the wrong year?
A common cause is confusing seconds with milliseconds. Passing a seconds-based timestamp directly to JavaScript's Date constructor makes it interpret the value as milliseconds. Multiply Unix seconds by 1,000 before creating the date.
How do I convert a Unix timestamp to ISO 8601 in JavaScript?
For a timestamp in seconds, multiply it by 1,000 and call toISOString() on the resulting date.
const timestamp = 1760000000;
const isoDate = new Date(timestamp * 1000).toISOString();
console.log(isoDate);
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Convert Timestamps with Confidence
Understand Unix seconds, JavaScript milliseconds, and ISO 8601 date strings to make debugging APIs, inspecting logs, and working with dates easier. Always confirm the timestamp unit and intended time zone before relying on a converted result.
JavaScript Timestamp Converter · Unix epoch conversion · Date and time development reference
