About online Unix timestamps
A Unix timestamp (POSIX time) counts the seconds from 1970-01-01 00:00:00 UTC—the “Unix epoch.” Leap seconds are not added to this count, so it is not identical to every astronomical clock, but it is what APIs, logs, and databases usually store.
This page converts epoch seconds or milliseconds into one line of local date/time in your browser. Nothing is uploaded.
Online Unix timestamp converter capabilities
Definition
Unix time is the number of seconds since the epoch instant. In ISO 8601 that instant is 1970-01-01T00:00:00Z. One hour is 3,600 seconds; one day is 86,400 seconds (leap seconds are not counted in Unix time).
Seconds vs milliseconds
- Typical log and JWT fields use 10-digit seconds.
- JavaScript Date.now() and many mobile APIs use 13-digit milliseconds.
- This tool treats values below 1e12 as seconds and larger integers as milliseconds.
Time zones and China (CST)
Display uses your site language locale (en-US or zh-CN). China Standard Time is UTC+8 today with no daylight saving. Historically, mainland China observed DST from 1986 through 1991 (clocks advanced one hour in summer); it has not been used since 1992.
JDK / IANA timezone data
When you format timestamps in Java, the result depends on the JRE’s timezone database (tzdata). Rules for Asia/Shanghai—including old DST transitions—were corrected across JDK releases (early data sometimes assumed midnight instead of 02:00 local for switches). Always test with the JDK version you ship.
Common use cases
API & access logs
Turn epoch fields in JSON or Nginx logs into readable local time during incidents.
JWT exp / iat
Compare exp (seconds) with “Now” before blaming clock skew or TTL misconfiguration.
Legacy 32-bit epochs
Spot values near 2,147,483,647 when auditing systems still using signed 32-bit time (Year 2038).
Frequently asked questions
- Does Unix time include leap seconds?
- No. Unix/POSIX time assumes every day has exactly 86,400 seconds. Leap seconds are handled (or ignored) outside the raw counter—so