ISO 8601 is the international standard for representing dates and times, such as 2026-05-29T12:00:00.000Z. It avoids ambiguity by ordering fields from largest to smallest.

What is the basic format?

The basic format removes the separators, giving a compact string like 20260529T120000Z, which is sometimes required by file names or older systems.

What does the Z at the end mean?

The Z is the "Zulu" designator meaning UTC — zero offset from Coordinated Universal Time. A string ending in Z, like 2026-05-29T12:00:00.000Z, is an explicit UTC timestamp with no ambiguity about the time zone.

What is the difference between UTC and local output?

The UTC variant converts your date to Coordinated Universal Time and appends Z. The local variant keeps your machine's wall-clock time and appends the offset, such as +01:00, so both describe the same instant in different notations.

What is an ISO week date?

The ISO week date expresses a day as year-Wweek-weekday, for example 2026-W22-5 for the Friday of week 22. It is based on ISO 8601 weeks that start on Monday, with week 1 containing the year's first Thursday.

Is anything uploaded?

No. The formatter uses the browser's native Date and Intl APIs locally, so your dates never leave the page.

ISO 8601 Date Formatter

ISO 8601 date formatter

Type any date — an ISO string, a casual format, or just “use now” — and get back a clean, standards-compliant ISO 8601 representation in several variants. ISO 8601 is the international standard for dates and times, used in APIs, logs, databases and file names because it orders fields from largest to smallest and sorts correctly as plain text.

How it works

Your input is parsed with the browser’s native Date, then formatted using Date and Intl APIs into multiple ISO 8601 forms. Choosing UTC converts to Coordinated Universal Time and appends Z; choosing local keeps your wall-clock time and appends your offset (e.g. +01:00).

Variant	Example
Full UTC	2026-05-29T12:00:00.000Z
Local with offset	2026-05-29T13:00:00.000+01:00
Date only	2026-05-29
Basic (no separators)	20260529T120000Z
ISO week date	2026-W22-5

Example

Entering 29 May 2026, 12:00 UTC produces the full string 2026-05-29T12:00:00.000Z, the date-only 2026-05-29, the basic 20260529T120000Z, and the week date 2026-W22-5 (Friday of week 22).

Each output is one click to copy, and everything runs in your browser, so nothing is uploaded.