Unix Timestamps, Milliseconds, and Time Zones
Auto-detect Unix seconds or milliseconds and convert among local time, UTC, ISO 8601 and multiple IANA zones with relative time.
What to know before you start
A timestamp is an instant, not a city time zone. Historical/future local display depends on IANA time-zone rules and daylight-saving changes.
Recommended workflow
- Identify whether your source uses seconds, milliseconds or an ISO string.
- Convert to UTC and the target IANA zone, then check whether daylight-saving changes the local clock time.
- When writing data back to an API, preserve the exact unit and document it explicitly.
How to check the result
Recheck the result against the original input and the rule you intended to apply. A timestamp is an instant, not a city time zone. Historical/future local display depends on IANA time-zone rules and daylight-saving changes.
Common mistakes
Common failures come from wrong units, ambiguous assumptions, changing the rule after seeing a result, or using a quick browser workflow where a regulated or specialist process is required.
Frequently asked questions
Why are some Unix timestamps 10 digits and others 13?
Modern timestamps in seconds are commonly around 10 digits, while milliseconds are commonly around 13. Always confirm the unit rather than relying only on length.
Does a Unix timestamp contain a time zone?
No. It identifies an instant relative to UTC; a time zone is applied only when displaying that instant as local time.
Unix Timestamp Converter
Auto-detect Unix seconds or milliseconds and convert among local time, UTC, ISO 8601 and multiple IANA zones with relative time.
Open the related toolUnix Timestamp Converter
Unix Timestamp Converter: A browser-based development and data utility with copyable or downloadable output.
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