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.

What is the ISO 8601 Date Formatter?

Format any date or time as ISO 8601 — full UTC, local with offset, date-only, basic format, and ISO week date. Copy-ready and fully client-side, so nothing is ever uploaded. It runs free in your browser on Gera Tools, with nothing uploaded.

ISO 8601 Date Formatter

Name: ISO 8601 Date Formatter
Creator: Gera Tools
License: https://creativecommons.org/licenses/by/4.0/

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

Worked example

Entering 29 May 2026, 12:00 UTC produces:

Full UTC: 2026-05-29T12:00:00.000Z
Local (if you are in UTC+1): 2026-05-29T13:00:00.000+01:00
Date only: 2026-05-29
Basic (no separators): 20260529T120000Z
ISO week date: 2026-W22-5 (Friday of week 22 of 2026)

Each output is one click to copy.

When to use each variant

Full UTC (2026-05-29T12:00:00.000Z) is the safest choice for storing timestamps in databases, writing API payloads, or logging events. The Z suffix means “zero offset from UTC” — unambiguous regardless of where the server or client is located.

Local with offset (2026-05-29T13:00:00.000+01:00) preserves the civil time that was in effect at a particular location. Use this when the local time matters — for example, flight schedules, legal deadlines, or calendar events that must display at a specific wall-clock time in a specific timezone.

Date only (2026-05-29) is appropriate when the time of day is irrelevant — a birthday, a filing date, a publication date. This form also sorts lexicographically in chronological order, which makes it ideal for filenames and database keys.

Basic format (20260529T120000Z) removes all separators. Some older systems, file naming conventions, and QR code payload formats require this compact form. It is valid ISO 8601 but harder for humans to read at a glance, so prefer extended format (with separators) in any context where readability matters.

ISO week date (2026-W22-5) is used in industries that schedule by week number — manufacturing, payroll, project planning, and logistics in Europe especially. The format is YYYY-Www-D where D is 1 (Monday) through 7 (Sunday). Note that the ISO week year can differ from the calendar year in early January and late December.

Why ISO 8601 sorts chronologically

ISO 8601 intentionally orders components from largest to smallest: year, then month, then day, then hour, then minute, then second. This means a simple ASCII sort of ISO 8601 date strings produces the correct chronological order — no special date parsing is needed. A filename like report-2026-06-01.pdf will always sort before report-2026-12-01.pdf in any file manager, terminal, or database ORDER BY clause.

Formats like 01/06/2026 or June 1, 2026 do not have this property, which is one reason ISO 8601 became the standard for technical use.

Everything runs in your browser, so nothing is uploaded.