How to use this tool
- Choose the conversion direction.
- For an epoch value, select seconds or milliseconds. For a date, include seconds and either Z or a timezone offset such as +05:30.
- Select Convert timestamp and compare the UTC date with both epoch representations.
Understanding the output
Unix time counts elapsed units from 1970-01-01T00:00:00Z. The output always shows UTC, avoiding dependence on the device’s local timezone. Fractional milliseconds are not accepted as timestamp input; ISO input can include up to three fractional-second digits.
If a timestamp appears inside a data payload, use the JSON Formatter to locate the field before converting its value.
The beginning of 2024
1704067200 seconds converts to 2024-01-01T00:00:00.000Z. The corresponding millisecond value is 1704067200000, exactly one thousand times larger.
Check the unit before diagnosing the date
An epoch value in milliseconds is much larger than one in seconds for the same moment. Interpreting a millisecond value as seconds can produce a date far outside the intended period, while interpreting seconds as milliseconds can place a modern event close to 1970. The tool requires an explicit unit instead of guessing from the number of digits.
Negative values represent times before the epoch. A timestamp is an instant, not a timezone label; a local clock representation depends on the timezone applied when displaying that instant.
Make timezone information explicit
A date string without a timezone can be interpreted differently by different systems. This converter requires Z or a numeric offset so the instant is unambiguous. It also rejects invalid calendar days rather than allowing a date such as February 30 to roll into the following month. Leap-second notation is outside the supported JavaScript date model.
Method and supported input
Integer timestamps are scaled to milliseconds and converted with the JavaScript Date API. ISO inputs undergo calendar checks before parsing, and the result is serialized as UTC.
- The epoch uses the conventional JavaScript/Unix representation without explicit leap seconds.
Limitations
- Supported dates are limited by JavaScript Date and safe integer input.
- Named timezones and daylight-saving rules are not accepted as input; use an explicit offset.
Common questions
Does the selected unit change an ISO date input?
No. ISO conversion always reports both seconds and milliseconds. The unit selector applies to numeric timestamp input.
Why is my local date different from the UTC output?
Your local timezone may be ahead of or behind UTC. Both representations can refer to the same instant.