Unix Timestamp Converter
Timestamp Converter turns a Unix epoch timestamp into a readable date and back again. It detects automatically whether your value is in seconds, milliseconds, microseconds or nanoseconds, and shows the result in UTC, in ISO 8601 and in your own timezone.
Runs entirely in your browser — nothing you enter is uploaded.
DeveloperUnits are told apart by size — a modern date is ~1.8 billion in seconds but ~1.8 trillion in milliseconds, so the two can't be confused. The date picker converts in your timezone; the same wall-clock time is a different timestamp in each zone.
About Unix timestamps
A Unix timestamp counts from midnight UTC on 1 January 1970 and identifies a single instant everywhere on earth, which is why systems store and exchange them instead of dates: there is no timezone to get wrong until a human needs to read it. Units are detected by magnitude, which works because they are three orders of magnitude apart — a present-day value is about 1.8 billion in seconds and about 1.8 trillion in milliseconds.
Mixing those units up is the classic timestamp bug, and it announces itself clearly: read milliseconds as seconds and dates land tens of thousands of years away; make the opposite mistake and everything happens in January 1970. Converting a date back to a timestamp does depend on a timezone, and the date picker here uses yours — worth remembering, because your server is very probably running on UTC.
Common questions
- How can I tell whether a timestamp is in seconds or milliseconds?
- By its length. A present-day timestamp has ten digits in seconds and thirteen in milliseconds, and the units are far enough apart that they cannot be confused. If a date comes out in 1970 you have read milliseconds as seconds; if it lands thousands of years in the future you have done the reverse.
- Do timestamps change between timezones?
- No, and that is the point of them. A timestamp counts from a fixed instant, so the same number means the same moment everywhere; only its rendering as a date depends on a zone. Converting in the other direction does depend on the zone, because a wall-clock time is a different instant in each one.
- What is the year 2038 problem?
- Systems that store Unix time in a signed 32-bit integer run out at 2,147,483,647, which is 03:14:07 UTC on 19 January 2038. A second later the value wraps to a large negative number and reads as December 1901. Modern 64-bit systems are unaffected, but embedded devices and legacy formats that fixed the width still need updating.
- Why does my date come out one day earlier than expected?
- Almost certainly because a bare date string such as 2026-09-02 is parsed as UTC midnight, which is the previous evening for anyone west of Greenwich. This tool builds dates from their parts so they are pinned to your local midnight instead. It is the single most common off-by-one-day bug in date handling.