Client-Side UtilityLocal memory execution • Zero server telemetry
Unix Timestamp Converter
Convert Unix epochs in seconds and milliseconds to universal UTC dates, ISO 8601 timestamps, and local browser time. Perform reverse date-to-timestamp conversions with explicit timezone handling.
DMaintained by Developer Tools
Published Last verified
Quick Presets:
Conversion Breakdown100% Client-Side Engine
Enter a Unix timestamp
Provide a timestamp in seconds or milliseconds, or click to convert.
Device Clock Time● Active
Seconds: ...Milliseconds: ...
Captured directly from your local device system clock (not a synchronized atomic server clock).
DMaintained by Developer Tools
Published Last verified
Calculation Methodology & Formula
Computes elapsed milliseconds since January 1, 1970 00:00:00 UTC (Unix Epoch) and formats target calendar instants using standard UTC methods and browser-resolved timezone offsets.
Date(timestamp * unitMultiplier)Worked Example: Unix Epoch Instant Zero
Convert timestamp 0 into UTC and ISO 8601 representations.
timestamp:0
unit:Seconds
Expected Output1970-01-01T00:00:00.000Z
The exact beginning of the Unix epoch.
Technical Constraints & Limitations
- JavaScript Date supports timestamps up to ±8,640,000,000,000,000 milliseconds (years -271821 to +275760).
- Current device time actions read from the local browser system clock, not an atomic NTP synchronized server.
Frequently Asked Questions
What is a Unix Timestamp?
A Unix timestamp is the count of seconds (or milliseconds) that have elapsed since the Unix epoch: 00:00:00 UTC on 1 January 1970, excluding leap seconds. It represents a universal instant in time that is identical anywhere on Earth.
Why do timestamps sometimes appear in seconds and other times in milliseconds?
Traditional Unix systems, POSIX APIs, Python, and databases often store timestamps in 10-digit seconds. JavaScript, Java, and modern web APIs frequently use 13-digit milliseconds for sub-second precision.
Does this tool send my timestamps or dates to a backend server?
No. All timestamp calculations, timezone resolutions, and ISO conversions are executed 100% locally in your web browser using standard ECMAScript Date APIs.