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Unix Timestamp Converter
Turn a Unix timestamp into a readable date, or a date into a timestamp. Seconds and milliseconds are detected automatically, and the result is given in local time, ISO 8601 and UTC so there is no ambiguity.
100% private — everything runs in your browser, nothing is ever uploaded.
What this tool does
A log line says a request failed at 1735689600, and an API you are integrating with stores the same moment as 1735689600000. Deciding whether a number is seconds or milliseconds by eye is a reliable way to land in the wrong year. This converter reads Unix timestamps in both units and gives the date in local time, ISO 8601 and UTC together, so there is no ambiguity about which zone a value refers to. It also works in reverse: type a date and get the timestamp to paste into a config file, a database query or a curl command. Developers use it when debugging scheduled jobs, checking token expiry claims, aligning log entries across services in different regions, or simply answering the question of what time a number in a spreadsheet actually means.
How to use it in three steps
- Paste a timestamp and press Convert to date, or type a date and press Convert to timestamp. Seconds and milliseconds are detected automatically from the length of the number.
- Use Now to fill both fields with the current time when you need a reference point for a test or a log entry.
- Read the local, ISO 8601 and UTC forms together before pasting the value into another system. Dates you type are read as YYYY-MM-DD HH:MM:SS in your own time zone. When writing a config value, note beside it whether the field expects seconds or milliseconds.
Questions people ask
How can I tell seconds from milliseconds?
A 10-digit number is usually seconds and a 13-digit number is milliseconds for dates in the current era. This tool detects that automatically, but values far in the past or future can be ambiguous, so check the resulting year before trusting it.
Why does the same timestamp show two different clock times?
A Unix timestamp is an absolute instant with no time zone attached. The local-time reading depends on your device's zone, while UTC and ISO 8601 give an unambiguous form. When sharing a value across teams, use the ISO or UTC string.
Does it handle dates before 1970?
Negative timestamps represent moments before the Unix epoch and can be converted, but many systems that consume timestamps do not accept them. If an integration rejects a negative value, store an ISO 8601 date instead.
Does a Unix timestamp include leap seconds?
Unix time counts seconds since the epoch without leap seconds, so it is a continuous scale rather than a literal UTC clock reading. That is convenient for arithmetic but means a timestamp cannot by itself express a leap second; systems that need one use a different representation.
Privacy: Timestamps and dates are converted by JavaScript in this browser tab using your own clock, and no log value, date or internal timestamp you enter is transmitted to a server.
How to use it
- Paste a timestamp and press Convert to date, or type a date and press Convert to timestamp.
- Use now fills both fields with the current time.
- Dates are read as
YYYY-MM-DD HH:MM:SSin your local timezone.
Why it stays private
Timestamps appear constantly in logs, which are among the more revealing artefacts a system produces. Converting them in a local page means no log line has to be handed over to be read.
Questions
What is a Unix timestamp?
The number of seconds that have elapsed since 00:00:00 UTC on 1 January 1970, ignoring leap seconds. It is the standard way computers record an instant in time, precisely because it carries no timezone ambiguity.
Is my timestamp in seconds or milliseconds?
You do not need to know — the tool detects it. Anything with an absolute value below 10^11 is treated as seconds and multiplied by 1000. In practice this correctly separates current-era seconds from milliseconds.
Which timezone does the local output use?
Whatever timezone your computer is set to. For anything that will be compared across machines, use the ISO 8601 or UTC line, since those include an explicit offset.
Why does my timestamp show a date in 1970?
Because seconds were fed in where milliseconds were expected, or the other way round. A millisecond timestamp read as seconds lands in January 1970 plus a few hours — 1,700,000,000 milliseconds is 21 January 1970, not the 2023 date it was meant to be. This is the single most common timestamp bug in application code, which is why the detection here is automatic and worth double-checking in your own program.
What happens in 2038?
Systems that store the timestamp as a signed 32-bit number run out of room on 19 January 2038 and overflow negative — the same class of bug as the Y2K rollover, and already fixed almost everywhere that matters. Anything running a current operating system or a modern language runtime is fine; ancient embedded hardware and very old databases are where the risk actually lives. As a rule, store timestamps as 64-bit integers and the question never arises.