Epoch Converter

The Epoch Converter transforms between Unix epoch timestamps (the number of seconds or milliseconds since 1 January 1970 UTC) and human-readable dates in any timezone. Unix timestamps are the universal internal representation of time in databases, APIs, log files, cache entries, JWT tokens, and almost every programming language. When you see 1704067200 in a log or 1704067200000 in a JavaScript debug output, you need to know that means 2024-01-01 00:00:00 UTC — and that is exactly what this tool tells you, instantly and correctly.

Both seconds and milliseconds timestamps are supported automatically — the converter detects which based on magnitude. Output includes the date in UTC and your local timezone, ISO 8601 format (2024-01-01T00:00:00Z), RFC 2822 format, common human-readable formats, and the relative time (\"2 years ago\" or \"in 37 days\"). Reverse conversion works too: type or pick any date, see the equivalent epoch timestamps in seconds and milliseconds, ready to paste into code or database queries. This is the daily tool of backend developers, data engineers, and anyone who spends time reading system logs.

Unix time counts seconds elapsed since the Unix epoch: 00:00:00 UTC on 1 January 1970. It is a simple integer, which makes date arithmetic trivial (subtraction gives seconds between events) and storage efficient (a single 64-bit integer per timestamp).

Unix time does not count leap seconds. Rare inserted seconds (26 since 1972) to keep UTC aligned with astronomical time are not included in Unix time by convention. This means Unix time is essentially equivalent to UTC minus leap seconds — for most practical purposes the difference is zero, but for astronomical or high-precision applications, leap seconds matter.

Seconds vs milliseconds: the original Unix timestamp is in seconds. JavaScript\u2019s Date.now() returns milliseconds (seconds × 1000). Database timestamps vary — some systems use seconds, others milliseconds, others microseconds or nanoseconds. The converter detects the unit from magnitude (values over 10 digits are likely milliseconds; values over 13 digits are likely microseconds or nanoseconds).

The 2038 problem: Unix timestamps stored as signed 32-bit integers overflow on 19 January 2038. Past that date, the integer rolls over to negative and date calculations break. Modern systems use 64-bit integers that will not overflow for 292 billion years. The converter works correctly past 2038, but any system using 32-bit epoch storage has a real bug to fix.

Negative timestamps represent dates before 1970. -1 is 31 December 1969 23:59:59 UTC. Valid but rare in real systems because most applications do not care about dates before Unix time began.

ISO 8601 is the international standard for date and time strings. The RFC 3339 variant (used in JSON APIs) looks like 2024-01-15T09:30:00Z where Z means UTC or +hh:mm for an offset. The converter outputs both forms.

Timezone conversion happens at display time — internally the tool keeps the timestamp as a pure UTC moment, then formats for the selected timezone using browser Intl APIs. This means DST is handled automatically for timezones that observe it, and the same timestamp displayed in different timezones gives the same moment viewed from different positions.

Compared to the Unix date command (date -d @1704067200), this tool provides multi-timezone output and multiple formats at once without requiring a shell. For scripting, use the CLI; for interactive debugging, the browser tool is faster.

Compared to Python\u2019s datetime.fromtimestamp() or JavaScript\u2019s new Date(), this tool does not require running code — paste a timestamp into a browser and see the result. It is especially useful when the timestamp you are investigating comes from a language you do not have installed locally.

Compared to built-in database date functions (PostgreSQL to_timestamp, MySQL FROM_UNIXTIME), this tool works without database access. When reading log files or API responses that contain timestamps, the browser tool is faster than SSHing into a database to run a query.