Unix timestamp converter
Convert between Unix timestamps and human-readable dates. ISO 8601, UTC, local, and relative-time outputs in your auto-detected timezone. All formatting via Intl APIs — runs entirely in your browser.
What is a Unix timestamp?
A Unix timestamp is the number of seconds (or milliseconds) elapsed since 00:00:00 UTC on 1 January 1970 — the "Unix epoch". Almost every modern system stores time this way internally because it's timezone-agnostic and trivially comparable. Converting between this raw number and a human-readable date is the most common timestamp-related task in software.
Seconds vs milliseconds
Older Unix systems and most language standard libraries use seconds. JavaScript's Date.now() returns milliseconds — that's the only major language that defaults to ms. Java's System.currentTimeMillis() also uses ms. When integrating systems, always check which precision the timestamp uses; mismatches produce dates 1000× off.
Timezones and Unix time
A Unix timestamp is timezone-independent — it always refers to the same instant in UTC. The timezone only matters when you convert it to a human-readable string. Two systems may print very different local times for the same timestamp without disagreeing about the moment.
Working with API responses? Try our JSON formatter.
Common Uses
- API debugging: When a server returns
created_at: 1745582400, paste it here to see the actual date in your timezone. - Cron expression sanity-checks: Verify scheduled task next-run timestamps before deploying to production.
- Log timestamp interpretation: Decipher Unix timestamps in log lines from web servers, syslog, or application logs.
- Database value inspection: Convert
created_atinteger columns from MySQL/PostgreSQL into local time during a debugging session. - Token expiry verification: Decode JWT exp claims and verify whether a token is currently valid.
- Migration script verification: Convert Unix epochs in CSV exports to ISO dates to confirm a database migration produced the right data.
- Cross-team time coordination: Convert "Slack message at 1745582400" into the local time of a colleague in another timezone.
FAQ
What is Unix time?
Unix time is a single integer counting seconds since 00:00:00 UTC on 1 January 1970, ignoring leap seconds. It's the lingua franca of digital timekeeping — every database, log file, and API uses it under some form.
How many seconds since 1970?
About 1.78 billion seconds as of mid-2026 — for the current value, use the "Use now" button. The number rolls over the 32-bit signed integer limit of 2,147,483,647 seconds on 19 January 2038, which is the famous Y2038 problem.
Milliseconds vs seconds — which does my system use?
Look at the magnitude. A 10-digit number is seconds (around year 2001+). A 13-digit number is milliseconds. JavaScript Date.now() and Java currentTimeMillis() use ms; most C/Python/Go APIs default to seconds. This tool auto-detects based on input length.
How do timezones interact with Unix timestamps?
They don't — Unix timestamps are always UTC. The timezone only affects how you display the timestamp as a date string. Two systems in different timezones print different "local" times for the same timestamp without disagreeing about the underlying instant.
What is the year-2038 problem?
Older 32-bit Unix systems store timestamps as signed integers, capping at 2,147,483,647 — which represents 03:14:07 UTC on 19 January 2038. After that, the value overflows and wraps to a negative number, breaking timestamp arithmetic. Most modern systems use 64-bit timestamps and are immune.
By the Numbers
- The Unix epoch starts at 00:00:00 UTC on 1 January 1970 — defined in POSIX (IEEE Std 1003.1)
- Most modern systems use 64-bit timestamps, valid until ~292 billion years from now
- The famous 2038 problem affects 32-bit signed timestamps, which overflow at 03:14:07 UTC on 19 January 2038
- JavaScript's
Dateuses milliseconds since epoch, with a valid range of ±100,000,000 days from 1 January 1970