DEVELOPER

ISO 8601 Converter

Convert an ISO 8601 date to Unix time and a readable date, or convert a Unix timestamp to ISO 8601, in one place.

ISO 8601 to Unix time

Unix time to ISO 8601

A two-way ISO 8601 tool

This page combines both directions of ISO 8601 conversion: paste an ISO 8601 string to get Unix seconds, Unix milliseconds and a readable date, or enter a Unix timestamp to get its ISO 8601 form in UTC and with your local UTC offset.

Recognised ISO 8601 forms

Both a date alone (2026-09-20) and a full date and time with Z or a numeric offset (2026-09-20T12:30:00+02:00) are accepted, with or without fractional seconds. A string with no offset is read in the time zone you choose, UTC by default.

Want the background? Read our comprehensive guide: ISO 8601 Date and Time Format.

How to use this tool

To convert ISO 8601 to Unix time: paste the string and select Convert to Unix.
To convert Unix time to ISO 8601: enter the timestamp and select Convert to ISO 8601.
Copy whichever result you need.
Use Use example to see a worked ISO 8601 string.

Examples

ISO 8601 to Unix time, and Unix time back to ISO 8601.

ISO 8601 to Unix

2026-09-20T12:30:00Z

Unix seconds: 1789907400
Unix milliseconds: 1789907400000

Unix to ISO 8601

1790000000000 (milliseconds)

ISO 8601: 2026-09-21T14:13:20.000Z

A date-only ISO 8601 string

2026-09-20

Read as: 2026-09-20T00:00:00.000Z

Frequently Asked Questions

What is ISO 8601?

The international standard format for writing dates and times, such as 2026-09-20T12:30:00Z, designed to sort correctly and never be mistaken for month/day versus day/month.

Does this tool need a time zone offset in the string?

No. If the string has no offset, choose which time zone to assume; UTC is used by default, which is the safest choice for logs and data storage.

Can I convert a Unix timestamp to ISO 8601 here too?

Yes, the second part of this page does exactly that, showing both the UTC form (ending in Z) and the form with your local UTC offset.

Is milliseconds precision supported?

Yes, both directions keep fractional seconds down to the millisecond.