ISO Date Converter
Convert a device-local date and time into a UTC ISO 8601 string and Unix timestamps.
How to use
- Enter a date and time.
- Calculate.
- Review the UTC ISO string, Unix seconds/milliseconds, and local display.
Capabilities and scope
This tool shows how a `datetime-local` value becomes an actual instant and how that instant is represented in UTC ISO form.
How it works
A `datetime-local` string has no zone, so JavaScript `Date` parsing interprets it in the current browser's local time zone. `toISOString()` then converts that instant to UTC ISO 8601 form.
Example
On a Korea Standard Time device, 2026-01-01 09:00 corresponds to 2026-01-01T00:00:00.000Z.
Useful for
- Turn local time into a UTC ISO string
- Check a timestamp before sending it to an API
- Compare ISO and Unix representations of one instant
Before you use it
- There is no input time-zone selector, so interpretation depends on the browser device's local time-zone setting.
Standards and references
Frequently asked questions
Which time zone is used when the input has no Z?
The `datetime-local` value is interpreted in the browser device's local time zone.
What does Z mean in the ISO result?
It indicates the value has been normalized to UTC, offset +00:00.