Tool
Timestamp Converter
Convert between Unix timestamps in seconds or milliseconds and ISO-8601 instants.
Try it
This tool runs entirely in your browser. Nothing you type or paste is sent anywhere.
1735689600 is 2025-01-01T00:00:00.000Z (1735689600 seconds since the Unix epoch).
How it works
- Interpreted the value as seconds.
- Rendered the instant in ISO-8601 and as Unix seconds/milliseconds.
- Compared it with the reference instant to produce a relative time.
- Unix time is UTC and ignores leap seconds.
Usage
- Enter a numeric timestamp or an ISO-8601 instant.
- Choose the unit or leave it on auto-detect.
- Read the ISO-8601 value, Unix seconds/milliseconds, and relative time.
Examples
Epoch seconds at the 2025 boundary
{
"value": 1735689600,
"unit": "s",
"reference": "2026-01-01T00:00:00.000Z"
}ISO instant in the future
{
"value": "2030-06-01T12:00:00.000Z",
"reference": "2026-01-01T00:00:00.000Z"
}Limitations
Seconds, milliseconds, and the 1e12 line
Unix seconds for current dates are around 1.7e9 and milliseconds around 1.7e12. Auto-detect uses that gap: a magnitude of 1e12 or more is treated as milliseconds, anything smaller as seconds. Always set the unit explicitly when precision matters.
Frequently asked questions
- What is a Unix timestamp?
- The number of seconds (or milliseconds) since 1970-01-01T00:00:00Z, ignoring leap seconds.