Why does my date come back shifted by a few hours?

A date written without a timezone is read as your machine local time, which is usually right and occasionally is not. Write it with an explicit offset and the result is exact.

What is the difference between seconds and milliseconds?

Seconds is the Unix timestamp: ten digits counting from 1970. Milliseconds is the same instant with three more digits. JavaScript Date works in milliseconds, which is why APIs often hand you that one.

Why does it refuse some numbers?

A number past the range a date can represent has no calendar meaning. Rather than wrap around into a year in the far future, it is rejected.

Can it tell my timezone?

No. A browser only knows the offset the operating system reports, and it cannot know where you actually are.

Unix Timestamp Converter

Convert Unix timestamps to dates and dates to timestamps, both directions in one place.

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Unix Timestamp Converter goes both ways in one panel. Feed it a number and it prints the ISO string, the UTC form, your machine local form, and a readable local timestamp. Feed it a date and it prints seconds and milliseconds back. The old setup had one page per direction, which meant guessing which page held the conversion you wanted.

How to use

Pick the direction: timestamp to date, or date to timestamp.
Enter the number or the date text.
Read the ISO, UTC, and local readings together.

Features and limitations

Both directions sit in one panel, so there is no second page to find.
Numbers under the input are filled in for you, in seconds and milliseconds.
A number outside the range a date can represent is rejected rather than rolled over into a far-future year.
Dates written with slashes are accepted, because that is how most people type them.
Seconds and milliseconds come out of a date conversion together, so neither has to be recomputed by hand.

Limitation: Reads the timestamp and the date as written. It does not know your timezone, so a date without one is treated as your machine local time rather than UTC, and it cannot account for daylight saving in any past conversion.

Related tools

Date Difference Timer Stopwatch

Frequently asked questions

Usage, result, and limitation information for this tool.

Why does my date come back shifted by a few hours?: A date written without a timezone is read as your machine local time, which is usually right and occasionally is not. Write it with an explicit offset and the result is exact.
What is the difference between seconds and milliseconds?: Seconds is the Unix timestamp: ten digits counting from 1970. Milliseconds is the same instant with three more digits. JavaScript Date works in milliseconds, which is why APIs often hand you that one.
Why does it refuse some numbers?: A number past the range a date can represent has no calendar meaning. Rather than wrap around into a year in the far future, it is rejected.
Can it tell my timezone?: No. A browser only knows the offset the operating system reports, and it cannot know where you actually are.