An API timestamp whose unit is known
1700000000000 · milliseconds
Interprets the value as 2023-11-14T22:13:20.000Z and shows both Unix units, UTC and device-local representations, rather than assuming every long-looking number is a date in seconds.
🕐Unix Timestamp ConverterReady
Runs entirely in your browser. It never sends a timestamp or date to a server.
Current Unix timestamp in whole seconds
—
Loading the device clock…
Capability checkedVerified September 9, 2026
What works
- Treat up to 10 significant integer digits as seconds and 13 or more as milliseconds in auto mode, while stopping on ambiguous 11–12 digit integers
- Parse ISO date-time text with a required numeric or Z offset instead of delegating ambiguous strings to browser Date.parse
- Reject impossible calendar dates and device-local daylight-saving gaps, and report when a local wall-clock time occurs twice
Important limits
- A displayed device-local date depends on the current browser device's time-zone database and settings; UTC is the portable instant representation
- The auto detector intentionally refuses ambiguous widths rather than inferring whether a rare early millisecond or far-future second timestamp was intended
What the Unix Timestamp Converter does—and does not do
Exact supported inputs, outputs, limits, and primary sources for the current implementation.
Accepted input
- A signed decimal Unix timestamp interpreted explicitly as seconds or milliseconds, or in a conservative auto mode
- A native date-and-time picker value interpreted explicitly as this device's local time or UTC
- An ISO 8601 date-time with a required Z or ±HH:mm offset
Produced output
- UTC ISO 8601, UTC display, device-local display and offset, Unix seconds and milliseconds, UTC day of year, and ISO week-year/week
- An explicit unit decision, input errors, and notices for discarded sub-millisecond precision or ambiguous local fall-back times
- Current device time and relative-duration context after the page hydrates
Operational limits
- JavaScript Date stores whole milliseconds only and accepts about ±275,760 years from the Unix epoch
- The picker offers only device-local time or UTC; named IANA time zones and a choice between both occurrences of a fall-back hour are not available
- ISO text must include a complete date-time and explicit Z or ±HH:mm offset; date-only strings, locale formats, and natural-language dates are rejected
- The tool reports POSIX/Unix time conventions and does not model leap seconds as separately encoded instants
Known limitations
- A displayed device-local date depends on the current browser device's time-zone database and settings; UTC is the portable instant representation
- The auto detector intentionally refuses ambiguous widths rather than inferring whether a rare early millisecond or far-future second timestamp was intended
- The relative-time row is an elapsed-duration estimate, not a calendar-aware promise about months or years
- A converted timestamp does not establish the original system's clock accuracy, time zone, leap-second behavior, or application-specific unit convention
Standards and primary sources
Continue the workflow
Capability claims last reviewed September 9, 2026. Review dates describe the implementation audit, not content freshness by itself.
Use the Unix Timestamp Converter with the right expectations
Timestamp utilities often silently multiply the wrong unit or let a browser guess what an offset-free date string means. This converter deliberately separates seconds from milliseconds, refuses the ambiguous widths in between, and offers an explicit local-versus-UTC choice for a native picker. Its ISO text path requires a real offset, retains pre-1970 values, and reports UTC calendar details without pretending that a device-local display is a portable source of truth.
When it is the right tool
- Checking whether an API or log value is Unix seconds or JavaScript-style milliseconds without relying on a risky magnitude guess
- Turning a local appointment or test fixture into a timestamp while explicitly choosing device-local time or UTC
- Converting an ISO 8601 value with Z or a numeric offset into Unix seconds and milliseconds
- Inspecting pre-epoch timestamps, fractional seconds, UTC ISO weeks, and a device's offset at one specific instant
A deliberate choice
Tooleras keeps this page specific to the job above instead of claiming support for adjacent formats, platforms, or edge cases it cannot verify. Open the capability guide for the exact inputs, outputs, limits, and sources.
Checked examples
A portable ISO date-time
2024-01-15T14:34:56.789+02:00
Applies the explicit +02:00 offset to produce the same instant as 2024-01-15T12:34:56.789Z, without handing an ambiguous string to browser-specific date parsing.
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