Unix Timestamp Converter
Convert epoch timestamps to human-readable dates (UTC, IST, local, ISO 8601) and dates back to timestamps. Auto-detects seconds vs milliseconds. Everything runs in your browser.
About this tool
Converts Unix epoch timestamps into readable dates across UTC, IST (Asia/Kolkata), your local timezone and ISO 8601, plus a relative "how long ago" reading — and converts calendar dates back into epoch seconds and milliseconds. The unit is auto-detected from the number's magnitude (13-digit values are treated as milliseconds), with a manual override if you need it.
Nothing is sent anywhere — all conversions use your browser's own date engine, with no server, no upload, and no tracking of tool inputs.
Frequently asked questions
Are Unix timestamps UTC?
Yes. A Unix timestamp counts seconds since 1970-01-01T00:00:00Z (the epoch) and is completely timezone-independent — the same instant is the same number everywhere on Earth. Timezones only enter the picture when you render it as a calendar date. That is what makes epoch time the safest format for storing and exchanging times; convert to local time only at display. The Timezone Converter on this site handles the display side.
What is the Year 2038 problem?
Systems that store Unix time in a signed 32-bit integer overflow at 2,147,483,647 — which is 2038-01-19T03:14:07Z. One second later the value wraps negative and reads as December 1901. Modern 64-bit operating systems, databases, and languages are unaffected, but embedded devices, old file formats, and legacy protocols that hard-code 32-bit time fields can still break.
Does Unix time include leap seconds?
No. Unix time pretends every day is exactly 86,400 seconds. When UTC inserts a leap second, Unix time either repeats a second or the system smears the extra second across nearby hours (as Google and AWS clocks do). Consequence: subtracting two Unix timestamps can be off by the handful of leap seconds that occurred between them — irrelevant for most apps, critical for astronomy and precise interval math.
How do I tell seconds from milliseconds?
By magnitude: timestamps for present-day dates have 10 digits in seconds (e.g. 1700000000) and 13 digits in milliseconds. JavaScript's Date.now() returns milliseconds while most Unix APIs and JWT claims use seconds — mixing them up puts you in 1970 or in the year 56000. This tool auto-detects the unit from the number's size, with a manual override.
Why does the same timestamp show a different date on another machine?
The timestamp is identical — the rendering differs because each machine formats it in its own local timezone, and near midnight that can even change the calendar date. This is the classic "off by one day" bug in date pickers and reports. Compare instants in UTC or as raw epoch values, and only localize at the final display step.