Time & Date · Timestamps
Unix Timestamp Converter
Convert a Unix timestamp (seconds, milliseconds, or microseconds since 1970-01-01 00:00:00 UTC) to a readable date and time, or convert a date/time back into a Unix timestamp — in UTC or any IANA timezone.
How this is calculated
timestamp = (date − 1970-01-01T00:00:00Z) in seconds
- date
- The instant being converted
- 1970-01-01T00:00:00Z
- The Unix epoch, the reference point in UTC
A Unix timestamp counts the number of seconds that have elapsed since the Unix epoch (midnight UTC on January 1, 1970), ignoring leap seconds. Because it's timezone-agnostic at its core, the same timestamp represents the same instant everywhere — only its human-readable rendering changes by timezone.
Assumptions & sources
- Unix time counts seconds since 1970-01-01 00:00:00 UTC and ignores leap seconds, like virtually all computer systems.
- Negative timestamps are dates before 1970. Microsecond values beyond millisecond precision are rounded to the millisecond.
- 1POSIX.1-2017 — Seconds Since the Epoch (Base Definitions, 4.16) — The Open Group / IEEE Std 1003.1
- 2ISO 8601 — Date and time format (week numbering, calendar dates) — International Organization for Standardization
- 3Calendrical Calculations (Reingold & Dershowitz) — Cambridge University Press
Calculator ID TIME-UNIX-001 · version 2.0.0
Common questions
Why does my timestamp have 13 digits instead of 10?
13-digit values are typically milliseconds, not seconds — divide by 1000 to get seconds. This tool detects that automatically and warns you.
Does this account for leap seconds?
No — Unix time by definition ignores leap seconds, which is standard behavior matched by virtually all systems.
What is the year 2038 problem?
Systems that store Unix time in a signed 32-bit number overflow after 03:14:07 UTC on 19 January 2038 (timestamp 2,147,483,647). Modern systems use 64-bit time, which lasts billions of years.