Unix Timestamp Converter
Convert epoch seconds or milliseconds to human-readable date/time and back. Shows UTC, local browser time, IST (Asia/Kolkata), and a configurable timezone.
Current Unix Timestamp
Milliseconds: 1778701657000
Timestamp → Date
Enter a timestamp above.
Date → Timestamp
Pick a date and time above.
Runs entirely in your browser — nothing is uploaded or logged.
How Unix timestamps work
A Unix timestamp is the number of seconds (or milliseconds) that have elapsed since the Unix epoch: 1970-01-01 00:00:00 UTC. Leap seconds are not counted, making it a perfectly uniform, monotonic counter — unlike wall clocks which occasionally jump or repeat.
// JavaScript Date.now() // → milliseconds since epoch (13 digits) Math.floor(Date.now()/1000) // → seconds since epoch (10 digits) new Date(1700000000 * 1000).toISOString() // → "2023-11-14T22:13:20.000Z" // Python import time int(time.time()) # → seconds time.time() * 1000 # → milliseconds
This tool uses the browser's built-in Intl.DateTimeFormat API with the timeZone option to render any timestamp in any IANA timezone without external libraries. The Intl.RelativeTimeFormatAPI produces the “3 hours ago” / “in 2 days” strings.
Frequently asked questions
Seconds or milliseconds — how do I tell?▼
Unix timestamps before ~year 2286 in seconds are 10 digits; in milliseconds they are 13 digits. Most server APIs and databases use seconds; JavaScript's Date.now() uses milliseconds. If unsure, paste 1700000000 — if it converts to November 2023, it's seconds; if the year shows 1970, you passed milliseconds as seconds.
What is Unix time?▼
Unix time (also called epoch time or POSIX time) counts the number of seconds elapsed since 1970-01-01 00:00:00 UTC, not counting leap seconds. It is a uniform, monotonic count used in databases, log files, HTTP headers, JWTs, and virtually every API that needs to represent a point in time.
Timezone confusion — why does the same timestamp show different dates?▼
Unix timestamps are inherently UTC — they represent a single, unambiguous instant in time. The displayed date and time change by timezone only because formatting applies a local offset. The timestamp 1700000000 is the same moment everywhere on Earth; only its human-readable representation differs.
Why does the year 2038 matter?▼
Systems storing Unix time as a signed 32-bit integer overflow on 2038-01-19 at 03:14:07 UTC, wrapping to negative values. This tool uses 64-bit JavaScript Numbers which can represent timestamps up to roughly year 285,000 without overflow — but legacy embedded systems, databases, and old C code using int32_t still face the problem.
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