Tool Overview
This tool converts a Unix timestamp into human-readable dates and times. You enter a number that is either seconds or milliseconds since the Unix epoch. The tool shows the same moment in UTC, in your local timezone, and in a timezone you pick from a list. It also shows how long ago or from now that moment is and gives the date in ISO 8601 and RFC 2822 formats. So you see one timestamp in several useful forms.
Developers and support staff often get timestamps from logs, APIs, or databases. A raw number like 1700000000 is hard to read. You need to know if it is in seconds or milliseconds and what timezone to use. This tool takes the number and shows the date and time in UTC, local time, and one other timezone. It detects seconds vs milliseconds by the length of the number. So you can quickly see what time a timestamp means.
The tool is for anyone who works with Unix timestamps. You do not need to be an expert. You enter a number, pick an optional timezone from the list, and read the results. An optional feature lets you type a natural language phrase (for example next Sunday morning) and the tool tries to turn it into a timestamp; that feature can fail and the main conversion does not depend on it.
Background & Concept Explanation
A Unix timestamp is the number of seconds or milliseconds since January 1, 1970 at midnight UTC. Many systems store time this way because it is one number and easy to compare. Seconds timestamps are often 10 digits (for example 1700000000). Millisecond timestamps are 13 digits (for example 1700000000000). The same moment in time can be shown in different timezones. UTC is the reference (GMT+0). Your local timezone is the one your device uses. You can also want to see the time in another place, for example New York or Tokyo.
When you have only a number you must know the unit. If you treat milliseconds as seconds you get a wrong date. This tool decides the unit by the length of the number you type. If it has 10 digits or fewer (ignoring a minus sign) the tool treats it as seconds. If it has more than 10 digits the tool treats it as milliseconds. So you do not have to choose; the tool picks for you. A related operation involves converting Unix timestamps as part of a similar workflow.
The tool shows the date and time in three ways: UTC, your browser local time, and one custom timezone from a dropdown. The dropdown has a fixed list of cities and regions (for example America/New_York, Europe/London, Asia/Tokyo). You cannot type a timezone name that is not in the list. The tool also shows a relative phrase like 2 hours ago or in 3 days using the current time. Finally it shows the same moment in ISO 8601 format (used in APIs and data) and RFC 2822 format (used in email). So you get both readable dates and standard formats.
People struggle when they convert by hand. They mix up seconds and milliseconds. They forget timezones. This tool does the conversion and shows UTC, local, and one other zone. You can copy any of the date strings. If the number is invalid or out of range the tool says so and does not show a result.
Key Features
- You enter a Unix timestamp in a text field. The field accepts a number in seconds or milliseconds. The tool allows up to 20 characters. If you enter more the tool shows an error message. The tool detects the unit automatically: 10 digits or fewer means seconds, more than 10 digits means milliseconds. So you type the number and the tool interprets it.
- A button sets the input to the current time as a timestamp in seconds. So you can quickly see what the current moment looks like in all formats. A clear button removes the input and hides the results. So you can start over.
- When the input is valid the tool shows three date rows. The first is UTC (GMT+0) with the date and time in UTC. The second is Local Time with the date and time in your browser timezone and the offset (for example GMT+01:00). The third is a custom timezone: you choose one from a dropdown (UTC, New York, London, Tokyo, and others). The tool shows the date and time in that zone and its offset. So you see the same moment in UTC, local, and one other place.
- An info line says whether the timestamp was interpreted as seconds or milliseconds and shows a relative time phrase (for example 2 hours ago or in 5 days). So you know the unit and how the time relates to now.
- Two format lines show ISO 8601 and RFC 2822. You can copy each with a copy button. ISO 8601 is the standard used in many APIs. RFC 2822 is often used in email headers. So you can paste the format you need.
- If the input is not a valid number or is outside the allowed range the tool shows Invalid timestamp format. The allowed range is from year 1 to year 9999. Negative timestamps (before 1970) are allowed within that range. So you know when to fix the input.
- An optional AI Natural Time Parser section has a button to open it. You type a phrase like Next Sunday morning or Yesterday 5pm in a text field (up to 200 characters). You click Parse. The tool sends the phrase to a remote service. If the service returns a timestamp the tool sets the main input to that value. If it fails you see an error (for example Failed to parse time. Try something simpler like Next Friday at 3pm or Input too long. Please use a shorter description). 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 server log (for example 1700000000). You paste it into the field. The tool shows the date and time in UTC, local, and the custom timezone you chose. You read the UTC row to confirm the moment. You copy the ISO 8601 string for a report or API.
You have a timestamp in milliseconds from an API response. You paste the 13-digit number. The tool detects milliseconds and shows the correct date. You pick a timezone from the dropdown (for example Asia/Tokyo) to see the time there. You copy the Tokyo time string. For adjacent tasks, converting text case addresses a complementary step.
You want to know the current time as a Unix timestamp. You click the button that sets the input to the current time. You see the timestamp value and all conversions. You copy the timestamp or the ISO string for your code or ticket.
You are debugging and need to see a timestamp in your local time and in UTC. You enter the number. You read the UTC row and the Local Time row. The relative time line (for example 3 hours ago) helps you see how old the event is.
You want to try a natural language phrase. You open the AI Natural Time Parser, type Next Friday at 3pm, and click Parse. If it works the main input is set to the matching timestamp and you see all conversions. If it fails you see an error and you can enter a timestamp by hand instead.
How to Use This Tool
- Open the Timestamp Converter in your browser.
- Enter a Unix timestamp in the input field. Use a number in seconds (up to 10 digits) or milliseconds (13 digits). You can use a negative number for dates before 1970. The tool accepts up to 20 characters. The tool will treat 10 digits or fewer as seconds and more as milliseconds.
- Optionally click the button that sets the input to the current time in seconds. Optionally click clear to remove the input and results.
- If the input is valid you see three rows: UTC (GMT+0), Local Time (your browser timezone), and a row with a timezone dropdown. Use the dropdown to pick a timezone (for example America/New_York, Europe/London, Asia/Tokyo). The date and time for that zone appear next to it.
- Read the info line to see whether the value was interpreted as seconds or milliseconds and to see the relative time (for example 2 hours ago). Read the ISO 8601 and RFC 2822 lines. Use the copy button next to any value to copy it to the clipboard.
- If you see Invalid timestamp format check that the input is a number and that it is within the allowed range (year 1 to 9999). Remove any letters or spaces. If you see a message about maximum characters reduce the input length.
- Optionally open the AI Natural Time Parser, type a short phrase (for example Next Sunday morning), and click Parse. If the service succeeds the main input is updated and you see the conversions. If you see an error the main conversion still works with whatever timestamp is in the field.
Calculations & Logic
The tool reads your input as a number. It trims spaces. If the number has 10 digits or fewer (not counting a leading minus) the tool treats it as seconds since the Unix epoch. If it has more than 10 digits the tool treats it as milliseconds. The tool multiplies seconds by 1000 to get milliseconds internally. It then builds a Date from that value. When working with related formats, converting currencies can be a useful part of the process.
The allowed range is from year 1 to year 9999. For seconds the minimum is minus about 62 billion and the maximum is about 253 billion. For milliseconds the range is the same in milliseconds. If the number is outside that range the tool marks the input invalid and does not show a result. So the date is always within a safe range.
UTC date and time use the UTC timezone (offset GMT+00:00). Local date and time use the timezone reported by your browser. Custom date and time use the timezone you picked from the dropdown. The tool uses a fixed list of timezone names (for example America/New_York, Europe/London). If a timezone name fails the tool falls back to UTC for that row. Dates are shown as year-month-day hour:minute:second in 24-hour form.
The relative time (for example 2 hours ago) is computed from the timestamp to the current time. It uses a standard function that adds a suffix like ago or in X days. So you see how far in the past or future the moment is.
ISO 8601 is the full ISO string from the Date (for example 2023-11-15T12:00:00.000Z). RFC 2822 is the UTC string from the Date (for example Wed, 15 Nov 2023 12:00:00 GMT). Both are derived from the same moment. So the formats are consistent. In some workflows, converting Julian dates is a relevant follow-up operation.
Reference Tables or Scales
| Input |
Interpretation |
| Up to 10 digits (e.g. 1700000000) | Seconds since Unix epoch (Jan 1, 1970 00:00:00 UTC) |
| More than 10 digits (e.g. 1700000000000) | Milliseconds since Unix epoch |
| Limit |
Value |
| Max input length | 20 characters |
| Timestamp range | Year 1 to year 9999 (seconds or milliseconds) |
| AI Natural Time Parser input | Max 200 characters |
Timezones in the dropdown include UTC, Americas (New York, Chicago, Denver, Los Angeles, Phoenix, Toronto, Vancouver, Mexico City, São Paulo, Buenos Aires), Europe (London, Paris, Berlin, Rome, Madrid, Amsterdam, Stockholm, Moscow, Istanbul), Asia (Dubai, Karachi, Kolkata, Bangkok, Singapore, Hong Kong, Shanghai, Tokyo, Seoul), Australia (Sydney, Melbourne), and Pacific (Auckland).
Tips, Limitations & Best Practices
Use seconds for most Unix-style timestamps (10 digits). Use milliseconds when your source gives 13 digits. The tool picks the unit by length so you do not need to choose. If you get a wrong date check the length: 10 digits is seconds, 13 is milliseconds.
Keep the input within 20 characters. Very long numbers trigger an error. The timestamp must be in the range year 1 to 9999. Negative values are allowed for dates before 1970.
The custom timezone is only one at a time. You pick one from the dropdown. You cannot type a timezone that is not in the list. To see another zone change the dropdown and read the updated row. For related processing needs, converting to lowercase handles a complementary task.
Local time depends on your device or browser timezone. If you are in a different place the local row will not match. Use UTC for a shared reference and the custom zone for a specific city.
The AI Natural Time Parser is optional and can fail. You may see Failed to parse time or Input too long or Parsed timestamp is outside reasonable range. Use short phrases like Next Friday at 3pm. The main conversion always works with a numeric timestamp in the field.
Copy copies only the value you click (the timestamp, one of the date strings, ISO 8601, or RFC 2822). Copy the one you need for your document or code.
