Unix Timestamp Converter

About this unix timestamp converter

Convert decimal Unix seconds or milliseconds to local time, UTC and ISO 8601 using an explicit unit selector. Convert a local date back using the browser timezone.

How this tool works

Converts decimal Unix seconds or milliseconds to a millisecond-precision instant and displays local time, UTC and ISO 8601. Local date entry converts back to the selected timestamp unit using the browser timezone.

1. Enter a number in “Unix timestamp” and choose “Seconds” or “Milliseconds”.
2. Read “UTC” and “ISO 8601”; “Your local time” uses the browser timezone.
3. Edit “Local date and time” to update the number in the currently selected unit; seconds and milliseconds in the date field are preserved.
4. Use “Use current time” to load the device clock, then confirm the unit required by the destination system.

Worked example

Limits and verification

Choose seconds or milliseconds explicitly; changing the unit reinterprets the entered number. Decimal parsing preserves whole milliseconds and truncates smaller fractions toward zero. The inclusive range is ±8640000000000000 milliseconds (±8640000000000 seconds). Trimmed input is limited to 4096 characters; exponent notation, a leading plus sign and non-decimal text are rejected. The local date field supports positive years only. UTC and ISO output also support zero and negative years. JavaScript dates do not represent leap seconds. Browser timezone data determines historical and daylight-saving offsets; this is not an atomic-time or GPS-time converter.

Examples demonstrate an expected workflow; they do not prove every input or every branch of an external specification. Check important results with an independent source before using them for money, security, compliance, safety, or irreversible file changes.

Browser processing boundary

Tool input is processed by code running in the browser and is not intentionally sent to a CZOA processing API. The page can still request ordinary site assets, analytics, or advertising when those services are enabled. Browser extensions and managed-device software remain outside this tool's control.

Relevant references

These references govern or help explain the format, protocol, or calculation used here. Listing a reference does not claim certification or complete implementation of every optional feature.

• ECMAScript Date: TimeClip and Date Time String Format
• HTML: Local Date and Time state (datetime-local)

Content owner: CZOA Tools · Review methodology

How to use it

1. Enter a number in “Unix timestamp” and choose “Seconds” or “Milliseconds”.
2. Read “UTC” and “ISO 8601”; “Your local time” uses the browser timezone.
3. Edit “Local date and time” to update the number in the currently selected unit; seconds and milliseconds in the date field are preserved.
4. Use “Use current time” to load the device clock, then confirm the unit required by the destination system.