タイムスタンプ変換

A Unix timestamp is the number of seconds that have elapsed since 1 January 1970 at midnight UTC, a moment known as the epoch. Because it is just a count from a fixed point in UTC, it represents an exact instant with no time zone attached, which is why logs, APIs and databases love it.

It turns an epoch value into a readable date and a date back into an epoch, showing the result as UTC, your local time, an ISO 8601 string and a human relative description like "3 hours ago". A Now button fills in the current time.

Seconds and milliseconds are detected automatically: a 10-digit number is read as seconds and a 13-digit number as milliseconds, which covers almost everything you will paste from a log or an API response.

Timestamps beat formatted date strings for storage and exchange because they are unambiguous, easy to sort and independent of time zone or locale. The usual pattern is to store the timestamp and convert it to a local, formatted date only when you display it to a person.

ISO 8601 (for example 2026-06-30T14:05:00Z) is the international standard text format for dates and times; the trailing Z means UTC. The relative value is handy for quickly judging how old a log line or record is.

One thing to know: systems that store Unix time in a signed 32-bit integer overflow on 19 January 2038, the so-called Year 2038 problem. Modern 64-bit systems are unaffected. Everything here runs in your browser, so nothing you enter is uploaded.