Convert Unix epoch timestamps in seconds, milliseconds, microseconds, and nanoseconds to ISO 8601 dates in UTC and your local time, and back.
Current time
“Now” reads the browser clock at millisecond precision, so its µs and ns values end in zeros.
Supported range: 0001-01-02T00:00:00Z to 9999-12-30T23:59:59.999999999Z.
A Unix timestamp, also called epoch time or POSIX time, counts the seconds since the Unix epoch:
1970-01-01T00:00:00Z, ignoring leap seconds. Values before 1970 are negative.
A timestamp names the same instant everywhere. Time zones matter only when you format it as a calendar date, which is why the converter shows both UTC and your local time.
ISO 8601 is the international standard for writing dates and times, such as
2026-11-12T19:04:59.737Z. The Z suffix means UTC; an offset like
+07:00 means local time that far ahead of UTC. RFC 3339, used by most APIs and JSON, is
a strict profile of ISO 8601.
A date and time without Z or an offset doesn’t identify a single instant, so the
converter asks you to add one or use Local mode.
Count the digits. For dates between 2001 and 2286, each unit has a fixed length:
| Unit | Digits | Example | Common in |
|---|---|---|---|
| Seconds (s) | 10 | 1794510299 |
Unix date, PHP, Go Unix(), JWT exp and iat |
| Milliseconds (ms) | 13 | 1794510299737 |
JavaScript Date.now(), Java, Kotlin, Dart, Firebase Remote Config |
| Microseconds (µs) | 16 | 1794510299737000 |
Databases, logging and tracing systems |
| Nanoseconds (ns) | 19 | 1794510299737000000 |
Go UnixNano(), Python time.time_ns(), OpenTelemetry |
The converter never guesses the unit. If the digit count doesn’t match the unit you picked, it shows a hint with a one-click switch.
| Language | Seconds | Milliseconds |
|---|---|---|
| JavaScript | Math.floor(Date.now() / 1000) |
Date.now() |
| Python | int(time.time()) |
time.time_ns() // 1_000_000 |
| Swift | Int(Date().timeIntervalSince1970) |
Int(Date().timeIntervalSince1970 * 1000) |
| Kotlin | Instant.now().epochSecond |
System.currentTimeMillis() |
| Java | Instant.now().getEpochSecond() |
System.currentTimeMillis() |
| Dart | DateTime.now().millisecondsSinceEpoch ~/ 1000 |
DateTime.now().millisecondsSinceEpoch |
| Go | time.Now().Unix() |
time.Now().UnixMilli() |
| C# | DateTimeOffset.UtcNow.ToUnixTimeSeconds() |
DateTimeOffset.UtcNow.ToUnixTimeMilliseconds() |
| PHP | time() |
(int) floor(microtime(true) * 1000) |
| PostgreSQL | floor(extract(epoch from now()))::bigint |
floor(extract(epoch from now()) * 1000)::bigint |
| Shell | date +%s |
date +%s%3N (GNU) |
Systems that store Unix seconds in a signed 32-bit integer overflow after
2147483647, which is 2038-01-19T03:14:07Z. The next second wraps to a
negative value and reads as 1901. 64-bit timestamps avoid this.
No. Every conversion runs locally in your browser with integer BigInt arithmetic, so
nanosecond values round-trip exactly. There’s no backend and no analytics.