ISO 8601-2-2019 amd1-2025 PDF

Full title and description

ISO 8601-2:2019/Amd 1:2025 — Date and time — Representations for information interchange — Part 2: Extensions — Amendment 1: Canonical expressions, extensions to time scale components and date time arithmetic. This amendment updates and extends ISO 8601-2:2019 with rules for canonical expressions, additional time-scale components and clarifications for date/time arithmetic intended for use in information interchange and data processing.

Abstract

This amendment supplements ISO 8601-2:2019 by defining canonical forms and additional extensions to the Part 2 representations. It covers clarifications and new material relating to canonical expressions of extended forms, expanded descriptions of time-scale components (for example explicit handling of particular time‑scale qualifiers and grouped units), and rules and examples for date/time arithmetic used in interchange contexts. The content is intended to improve unambiguous machine and human interpretation of extended date/time strings and interval arithmetic in systems implementing ISO 8601 extensions.

General information

• Status: Published
• Publication date: January 2025 (Edition 1, 2025-01)
• Publisher: International Organization for Standardization (ISO), via ISO/TC 154
• ICS / categories: 01.140.30 (Documents in administration, commerce and industry)
• Edition / version: Amendment 1 to ISO 8601-2:2019 — ISO 8601-2:2019/Amd 1:2025, Edition 1 (2025)
• Number of pages: 13

Scope

This amendment applies to ISO 8601-2:2019 and specifies additional representations and notational rules that extend the basic rules of ISO 8601-1. It refines canonical expression forms, extends the set of supported time-scale components and grouped units, and provides normative guidance and examples for date and time arithmetic and interval operations used in information interchange. It does not change the basic scope of ISO 8601-2 regarding Gregorian calendar dates and 24‑hour clock times, nor does it address non-Gregorian calendar encodings or character-encoding issues beyond representation syntax.

Key topics and requirements

• Canonical expressions for extended date/time representations to reduce ambiguity in interchange.
• Extensions to time-scale components and grouped units (clarified notation and qualifiers).
• Normative rules and examples for date/time arithmetic (addition, subtraction, rolling of units, interval arithmetic).
• Clarifications for representing uncertain, approximate or partially specified dates and times within the extensions framework.
• Guidance on repeat rules and extended interval representations when used in combination with canonical forms.

Typical use and users

This amendment is intended for standards implementers and systems that need precise, unambiguous extended date/time representations: software and API developers, database and data‑exchange architects, archivists and records managers, systems integrators, and organizations that exchange complex temporal data (e.g., scheduling, scientific measurement, legal records). It is particularly relevant where canonical forms and deterministic date/time arithmetic are required for interoperability, automated processing or long‑term preservation.

Related standards

ISO 8601-2:2019 (Part 2: Extensions) — the amendment applies directly to this document. See also ISO 8601-1:2019 (Part 1: Basic rules) and earlier editions of ISO 8601 (2004) for historical context and baseline representations; implementers should use Part 1 and Part 2 together where extensions are required.

Keywords

ISO 8601, date and time, extensions, canonical expression, time scale, date arithmetic, intervals, recurring rules, time representation, information interchange, ISO/TC 154.

FAQ

Q: What is this standard?

A: It is Amendment 1 (2025) to ISO 8601-2:2019, providing canonical expressions and extensions for date/time representations and arithmetic for use in information interchange.

Q: What does it cover?

A: The amendment covers canonical forms for extended representations, additional time-scale components and grouped units, and normative guidance and examples for date/time arithmetic and extended intervals used when exchanging temporal data. It builds on the extensions already defined in ISO 8601-2:2019.

Q: Who typically uses it?

A: Software developers, API designers, database architects, records managers, standards bodies, and any organization or project that requires precise, machine‑readable extended date/time representations and deterministic arithmetic for interoperability.

Q: Is it current or superseded?

A: As of publication in January 2025 this amendment is published and applies to ISO 8601-2:2019. It is an active amendment; users should check for any further revisions or future work items replacing or extending Part 2.

Q: Is it part of a series?

A: Yes — it is part of the ISO 8601 family. Part 1 (ISO 8601-1:2019) contains the basic rules; Part 2 (ISO 8601-2:2019) contains extensions and this document is Amendment 1 to Part 2 (2025).

Q: What are the key keywords?

A: Canonical expression, date/time arithmetic, extensions, intervals, repeat rules, time scale components, ISO 8601, information interchange.