Unix Timestamp Converter: Decode Epoch Seconds, Milliseconds, and ISO Dates

TL;DR — The Unix Timestamp Converter handles seconds, milliseconds, and nanoseconds, in any time zone, with ISO 8601 output. For "what date is N days from now" use the Date Calculator; for "what time is it for the team in Tokyo right now" use the World Clock.

Why Unix time exists

A Unix timestamp is the number of seconds since 00:00:00 UTC on 1 January 1970 (the "Unix epoch"). One integer. No time zone. No leap years to special-case. No DST. It’s the universal time format every server, database, and protocol agrees on.

The cost: humans can’t read it. 1735689600 tells you nothing until you convert it.

Seconds vs milliseconds vs nanoseconds — quick distinguisher

Length	Unit	Used by
10 digits	Seconds	Unix tools, Postgres EXTRACT(EPOCH), most APIs
13 digits	Milliseconds	JavaScript Date.now(), Java, Android
16 digits	Microseconds	Some Python datetime ops
19 digits	Nanoseconds	Go, ClickHouse, observability tools

The converter auto-detects which one you pasted. The classic bug: treating a 13-digit JS timestamp as seconds and getting a date in the year 56000.

Convert a timestamp in 3 seconds

1. Open the Unix Timestamp Converter.
2. Paste a timestamp — type is auto-detected.
3. Read the human format, ISO 8601, and "time from now" (e.g. "2 hours ago").
4. Switch the time zone to verify the value in your locale and your server’s UTC.
5. For the reverse, pick a date and copy the epoch.

Copy-ready code samples

// JavaScript
Date.now();                              // ms since epoch
Math.floor(Date.now() / 1000);           // seconds since epoch
new Date(1735689600 * 1000).toISOString();

// Python
import time
int(time.time())                          // seconds
import datetime
datetime.datetime.fromtimestamp(1735689600, tz=datetime.timezone.utc)

// PostgreSQL
SELECT EXTRACT(EPOCH FROM now())::bigint;
SELECT to_timestamp(1735689600);

// Bash
date -u +%s                               // current
date -ud @1735689600                      // decode

The bugs Unix time still causes

• Year 2038 problem. 32-bit signed seconds overflow on 19 Jan 2038. Use 64-bit timestamps everywhere by now.
• Wrong unit at a boundary. Treating ms as seconds (or vice versa) silently produces dates 1000× off. Always check the digit count.
• Local-time epoch. Some languages have localtime conversions that mix UTC and TZ — pin to UTC explicitly.
• Leap seconds. POSIX time pretends leap seconds don’t exist. For sub-second-precision astronomy or finance, use TAI.

FAQ

How do I tell if a timestamp is seconds or milliseconds?

Count digits. 10 = seconds (good until 2286), 13 = milliseconds. The converter auto-detects.

What time zone is a Unix timestamp in?

None — it’s absolute UTC. Display in any zone by converting after parsing.

Does the converter work in my local time zone?

Yes — pick any IANA zone (America/New_York, Asia/Kolkata, etc.). It defaults to your browser’s zone.

How do I get the current Unix timestamp?

The converter shows it live at the top, updating every second.

Time-related tools

• Unix Timestamp Converter — epoch ↔ date, auto-detect units.
• Date Calculator — add/subtract days, weeks, months.
• World Clock — current time across cities.