Unix Timestamp Converter

Date and time ↔ Unix timestamp

This tool converts in both directions. Enter a date and time to get its Unix timestamp, or paste a timestamp to read the instant in UTC and in your browser’s local time zone.

The results always show:

• seconds since the Unix epoch;
• milliseconds since the Unix epoch;
• the UTC date in ISO 8601 format;
• local date and time with its UTC offset;
• the browser time-zone name, when available.

Run the conversion with the primary button, Ctrl+Enter on Windows and Linux, or Cmd+Enter on macOS.

What is a Unix timestamp?

A Unix timestamp represents the time elapsed since this instant:

1970-01-01 00:00:00 UTC

That origin is also called the Unix epoch. The value 0 identifies the epoch itself, 1 second identifies 1970-01-01 00:00:01 UTC, and -1 second identifies 1969-12-31 23:59:59 UTC.

A timestamp identifies an instant, not a display format. The same value can appear as a different clock time in Madrid, Mexico City or Tokyo while still representing one moment.

Verifiable example

The “Load example” action uses this date:

2000-01-01 00:00:00 UTC

Its exact conversion is:

946684800 seconds
946684800000 milliseconds
2000-01-01T00:00:00.000Z

The Z in the ISO output denotes UTC. Reverse the direction and convert 946684800 seconds to recover the same instant.

Converting a date and time

Select “Date and time → timestamp”, complete the date and choose how it should be interpreted:

• This browser’s local time: use the time zone configured on the device.
• UTC: treat the entered value as universal time with no offset.

A time alone cannot produce a timestamp. 14:30 occurs every day and means something different in every time zone, so the input also requires a date and an explicit time interpretation.

The date input accepts whole seconds. To preserve a subsecond fraction, use the timestamp mode and select milliseconds.

Converting a timestamp to date

Select “Timestamp → date and time”, enter the integer and choose its unit. The tool does not infer the unit from the number of digits because that assumption breaks for old dates, negative timestamps and values far from the present.

For example, these inputs represent the same instant:

946684800 s
946684800000 ms

Do not use thousands separators or exponents. Enter 946684800, not 946,684,800 or 9.466848e8.

Seconds or milliseconds

Systems commonly store Unix timestamps in one of these units:

1 second = 1,000 milliseconds

Seconds are enough for many logs, tokens and APIs. Milliseconds distinguish events within the same second and match the unit used by JavaScript Date.

When a millisecond value is not divisible by 1,000, the result in seconds keeps the exact fraction. For example:

-1 ms = -0.001 s

Local time, UTC and clock changes

UTC has no seasonal clock changes. Local time may move forward or backward for daylight saving, and those rules depend on the country and year.

During a forward change, a local time can be impossible. The tool rejects it instead of silently shifting it. During a backward change, one local time can occur twice; the browser chooses the first occurrence and the tool displays a warning so you can verify the UTC offset.

This version does not include a city selector. It uses UTC or the browser zone to avoid a heavy library of changing time-zone rules. If you need another zone, first convert the instant and then apply a suitable IANA time-zone source in your application.

Timestamps in JWT and JSON

Common JWT time claims such as exp, iat and nbf are normally expressed in Unix seconds. Read the header and payload with the JWT decoder, then paste one of those integers here to obtain a readable date.

If the timestamp belongs to a document, the JSON formatter helps inspect its structure. Do not switch between seconds and milliseconds without checking the contract of the API that produced the value.

Limits and precision

• Positive, zero and negative timestamps are supported.
• A timestamp must be a decimal integer no longer than 32 characters.
• Manual date input supports years from 0001 through 9999.
• Results stay within the temporal range implemented by browser Date.
• The timestamp is validated with exact integers before creating a date, avoiding silent floating-point loss.
• Unix time does not count leap seconds.
• Local output depends on the time-zone rules available to the browser and operating system.

Frequently asked questions

What is the timestamp right now?

Select “Use current time”. In date mode it fills the current clock time; in timestamp mode it enters the current value in the selected unit.

Should I use UTC or local time?

Use UTC when the source is already expressed in UTC or when the result must be independent of a device. Use local time only when the entered date genuinely belongs to the zone configured in your browser.

Why does my timestamp have 10 or 13 digits?

Current values often have about 10 digits in seconds and 13 in milliseconds, but length is not a guarantee. Select the unit defined by the system that produced the value.

Is my date sent or stored?

No. The conversion runs in this tab and the content disappears when you reload or close the page.