ISO-8601

ISO 8601. The international standard that has codified the representation of dates and times for information interchange since 1988.

Definition

ISO 8601 is the ISO standard that defines the standardised representation of dates and times in information exchange. It introduces the YYYY-MM-DD format for dates, hh:mm:ss for times, YYYY-MM-DDThh:mm:ssZ for UTC datetimes, plus durations (P3Y6M4DT12H30M5S) and intervals. It is universally adopted by EDI XML formats, JSON and databases.

Origin

ISO 8601 was first published in 1988, revised in 2000, 2004 and 2019 (Part 1 and 2). It supersedes ISO 2014 (date), ISO 3307 (time) and ISO 4031 (UTC). In EDIFACT, the DTM segment uses format Y4MDH (ISO 8601 without separators); in UBL and CII, xsd:date and xsd:dateTime elements follow ISO 8601.

Example in context

<cbc:IssueDate>2026-05-14</cbc:IssueDate>
<cbc:DueDate>2026-06-13</cbc:DueDate>

In a UBL 2.1 PEPPOL BIS Billing payload, every date is expressed in strict ISO 8601. EN 16931 mandates this format to guarantee European interoperability and unambiguous parsing across time zones.

Related terms

• DTM — EDIFACT date segment, aligned with ISO 8601.
• EN 16931 — the European norm that makes ISO 8601 mandatory for B2G invoicing.
• W3C XML Schema — xsd:date and xsd:dateTime are aligned with ISO 8601.