Epoch Converter

Tool Overview

This tool converts between epoch timestamps and human-readable dates and times. You enter either a number (epoch in seconds, milliseconds, microseconds, or nanoseconds) or a date string. The tool shows the same moment in local time and in UTC, and it shows the epoch value in seconds, milliseconds, and microseconds. So you can turn a raw timestamp into a date or a date into timestamps in several units.

Developers and support staff often see epoch numbers in logs, APIs, or databases. A number like 1736352000 or 1736352000000 is hard to read. You need to know the unit and the timezone. This tool accepts the number and detects the unit by how many digits it has. It shows local time (your browser timezone) and UTC. It also shows the same moment as seconds, milliseconds, and microseconds so you can copy the form you need. So you can quickly see what time an epoch is and get other units.

The tool is for anyone who works with epoch timestamps or date strings. You do not need to be an expert. You enter a number or a date, and you read the results. You can override the detected unit for epoch input. An optional AI Parse button tries to turn natural language into a date string; that feature can fail and the main conversion does not depend on it.

Background & Concept Explanation

An epoch timestamp is the number of seconds (or milliseconds, microseconds, or nanoseconds) since January 1, 1970 at midnight UTC. Many systems use seconds (10 digits) or milliseconds (13 digits). Some use microseconds or nanoseconds. The same moment in time can be written in any of these units. If you treat milliseconds as seconds you get a wrong date. This tool detects the unit by the length of the number you type. Up to 10 digits (or 11 with a minus) is seconds. Up to 13 is milliseconds. Up to 16 is microseconds. More is nanoseconds. So you do not have to choose the unit; the tool picks for you. You can change it with the unit buttons if the tool guessed wrong.

You can also enter a date string instead of a number. The tool accepts formats that the browser can parse (for example ISO 8601 like 2025-01-09T12:00:00Z or a simple date). It then shows that moment in local time and UTC and gives the epoch in seconds, milliseconds, and microseconds. So you can go from date to epoch as well as epoch to date. A related operation involves converting Julian dates as part of a similar workflow.

Local time uses your browser timezone. UTC is the reference (no offset). The tool shows a relative phrase like 2 hours ago or in 3 days so you see how far the moment is from now. The valid range for dates is year 1 to year 9999. Timestamps outside that range show an error. So the tool keeps everything in a safe range.

People struggle when they convert by hand. They mix up seconds and milliseconds. They use the wrong unit. This tool detects the unit and lets you override it. You see local time, UTC, and epoch in three units. You can copy any value. If the input is not a number or a parseable date the tool says so and does not show a result.

Key Features

• You enter a value in one field. The field accepts an epoch number (digits only, optional minus at the start) or a date string. The tool allows up to 30 characters. If you enter more the tool shows an error. So you type either a timestamp or a date.
• The tool detects what you typed. If it is a number it detects the unit by digit count: up to 10 digits is seconds, up to 13 is milliseconds, up to 16 is microseconds, more is nanoseconds. If it is a parseable date string it detects date. If it cannot tell it shows Format unrecognized. So you know what the tool thinks you entered.
• When the input is an epoch number the tool shows small buttons for seconds, milliseconds, and microseconds. You can click one to force that unit. So if the tool guessed wrong you can fix it. Nanoseconds is detected automatically but there is no button for it; the conversion still uses nanoseconds when the number is long enough.
• A Now button sets the input to the current time as a timestamp in seconds. So you can quickly see the current moment in all forms. The current epoch in seconds is also shown and updates every second elsewhere on the page when the input is empty.
• When the input is valid the tool shows two result cards. The first is Local Time: the date and time in your browser timezone, the timezone name, the offset (for example +01:00), and a relative phrase (for example 2 hours ago). The second is UTC Time: the same moment in UTC. Each card has a copy button. So you see the moment in local and UTC and can copy either.
• Below the cards the tool shows the epoch in three units: Seconds, Milliseconds, and Microseconds. Each has a value and a copy button. So you can copy the unit you need for your code or API. Nanoseconds is not shown in this row even when the input was in nanoseconds.
• If the input is invalid the tool shows an error. Examples: Input too long (over 30 characters), Format unrecognized (not a number or date), Invalid epoch value, Date out of valid range (year 1 to 9999), Invalid date format. So you know when to fix the input.
• Recent conversions are stored. When you have at least one conversion a history button appears. Click it to see the last 10 inputs. Click an item to load that input again. You can clear the history. So you can repeat a conversion quickly.
• When you have typed something an AI Parse button appears. Click it to send the input to a remote service. The service may return a date string and the tool sets the input to that. If it fails you see an error (for example Failed to parse natural language date or Unable to parse with AI at this time). The main conversion does not depend on this. So you can try natural language when the service is available.

Common Use Cases

You have a timestamp from a log (for example 1736352000). You paste it into the field. The tool detects seconds and shows local time, UTC, and the epoch in seconds, milliseconds, and microseconds. You read the local time to see when it was. You copy the milliseconds value for an API.

You have a 13-digit number from an API. You paste it. The tool detects milliseconds and shows the correct date. You check the relative time (for example 3 hours ago) to see how old the event is. You copy the UTC line for a report. For adjacent tasks, converting text case addresses a complementary step.

You want the current time as an epoch. You click Now. The input is set to the current timestamp in seconds. You see local time, UTC, and the three epoch units. You copy the seconds or milliseconds value for your script.

You have a date string (for example 2025-01-09T12:00:00Z). You paste it. The tool detects it as a date and shows local time, UTC, and the epoch in seconds, milliseconds, and microseconds. You copy the seconds value for a database or config.

The tool detected your number as milliseconds but it is actually seconds. You click the seconds button in the unit row. The result updates. You read the correct local time and copy the value you need.

You want to try a natural language phrase. You type something like next Friday at 3pm and click AI Parse. If the service returns a date the input is updated and you see the conversion. If it fails you enter an epoch or date string by hand. When working with related formats, converting currencies can be a useful part of the process.

How to Use This Tool

1. Open the Epoch Converter in your browser.
2. Enter a value in the input field. Use an epoch number (digits only, optional minus) or a date string the browser can parse. The tool allows up to 30 characters. For a number the tool will detect the unit: up to 10 digits is seconds, up to 13 is milliseconds, up to 16 is microseconds, more is nanoseconds.
3. Optionally click Now to set the input to the current time in seconds. Optionally click one of the example values below the field (when the field is empty) to try a sample.
4. If the input is an epoch number and the tool shows unit buttons (seconds, milliseconds, microseconds) click the one that matches your data if the tool guessed wrong. The result updates.
5. Read the two result cards. The first is Local Time (your timezone, offset, and relative time). The second is UTC Time. Use the copy button on a card to copy that date string. Read the row below with Seconds, Milliseconds, and Microseconds. Use the copy button next to any value to copy it.
6. If you see an error fix the input. Keep it under 30 characters. Use only digits (and an optional leading minus) for epoch, or a valid date string. Ensure the date is in the range year 1 to 9999.
7. Optionally open the history (button with clock icon when you have conversions). Click an item to load that input again. Optionally click AI Parse when you have input to try natural language parsing; if it fails the main conversion still works with what is in the field.

Calculations & Logic

The tool reads your input as a string. It trims spaces. If the string is only digits (and an optional leading minus) it is treated as an epoch number. The number of digits (ignoring the minus) decides the unit: 1–10 is seconds, 11–13 is milliseconds, 14–16 is microseconds, 17–20 is nanoseconds. If the digit count is over 20 the input is treated as unrecognized. The value is converted to milliseconds: seconds times 1000, milliseconds as-is, microseconds divided by 1000, nanoseconds divided by 1,000,000. That milliseconds value must be between minus about 62 trillion and about 253 trillion (year 1 to 9999). If it is outside that range the tool shows Date out of valid range and does not show a result.

If the input is not a number the tool tries to parse it as a date with the Date constructor. If the result is a valid date and the year is 1 to 9999 the input is treated as a date. The tool then uses that date to build the result. If parsing fails or the year is out of range the input is unrecognized.

From the moment in time (as a Date) the tool computes local time using your browser timezone (Intl), UTC time in a fixed format, and the epoch in seconds (floor of milliseconds divided by 1000), milliseconds, and microseconds (milliseconds times 1000, using BigInt where needed). The relative time (for example 2 hours ago) is the distance from that date to now with a suffix. So all outputs refer to the same moment.

The manual unit override (seconds, milliseconds, microseconds buttons) only affects epoch input. When you click a button the tool uses that unit to convert the number to milliseconds instead of the auto-detected unit. So you can correct a wrong guess. Nanoseconds has no button but is still used when the number has 17–20 digits. In some workflows, converting speed units is a relevant follow-up operation.

Reference Tables or Scales

The result shows epoch in seconds, milliseconds, and microseconds only. Nanoseconds is accepted as input but not shown in the result row. Copy copies the value you click (one of the date strings or one of the epoch numbers).

Tips, Limitations & Best Practices

Use the unit buttons when the tool guesses wrong. Many timestamps are 10 digits (seconds) or 13 digits (milliseconds). If you paste a 10-digit number and the date looks wrong in the future it might be milliseconds; click the milliseconds button to see. If the date is in the past and looks right leave it as seconds.

Keep the input within 30 characters. Epoch numbers with more than 20 digits are treated as unrecognized. The date must be in the range year 1 to 9999. Negative timestamps (before 1970) are allowed within that range.

For date strings use a format the browser accepts. ISO 8601 (for example 2025-01-09T12:00:00Z) works. Other formats may work depending on the browser. If you see Invalid date format try ISO or a simple date. For related processing needs, converting length units handles a complementary task.

Local time depends on your browser timezone. If you are in a different place the local card will not match. Use UTC for a shared reference. The relative time (for example 2 hours ago) is from the moment you are viewing to now.

AI Parse is optional and can fail. You may see Failed to parse natural language date or Unable to parse with AI at this time. Use short, clear phrases. The main conversion always works with an epoch number or a date string in the field.

History stores the last 10 conversions. Click an item to load that input again. Clear removes all history. The tool does not store history on the server; it is only in your browser session.