attestwireAttestwire › Rule reference › ATW-DATE-NOT-A-CALENDAR-DATE
ATW-DATE-NOT-A-CALENDAR-DATE Every date must be a real calendar date written as YYYY-MM-DD
noun · Attestwire · fatal · BT-2
For a sample invoice, the library reports: The invoice issue date (BT-2) is "09.08.2026", which is not a calendar date.
- Business term
BT-2- Severity
fatal
The fix
Set issueDate to an ISO 8601 calendar date — four-digit year, two-digit month, two-digit day, separated by hyphens, with no time part and no timezone. If you are formatting a JavaScript Date, note that toISOString() appends a time part that must be trimmed, and that it converts to UTC first, which can move the date by a day.
A passing value
"issueDate": "2026-07-31"What the library returns
The full error returned by @attestwire/en16931. It includes the rule ID,
affected field and suggested correction. Developers can use this object in their application:
{
"rule": "ATW-DATE-NOT-A-CALENDAR-DATE",
"field": "BT-2",
"severity": "fatal",
"message": "The invoice issue date (BT-2) is \"09.08.2026\", which is not a calendar date. UBL types this element as xs:date, so the only accepted form is a zero-padded YYYY-MM-DD naming a day that actually exists: \"31.07.2026\" and \"07/31/2026\" fail on syntax, and \"2026-02-30\", \"2026-13-01\" and \"2025-02-29\" fail because no such day is on the calendar. Core EN 16931 has no BR-* rule for it because the XML schema already forbids it — which is exactly why it is worth catching here. Left alone, this value passes every business rule, is written into the document verbatim, and the document is then rejected by schema validation before any validator reaches the business rules at all.",
"fix": "Set issueDate to an ISO 8601 calendar date — four-digit year, two-digit month, two-digit day, separated by hyphens, with no time part and no timezone. If you are formatting a JavaScript Date, note that toISOString() appends a time part that must be trimmed, and that it converts to UTC first, which can move the date by a day.",
"example": "\"issueDate\": \"2026-07-31\"",
"xpath": "/ubl:Invoice/cbc:IssueDate",
"docsUrl": "https://github.com/attestwire/en16931#not-implemented-yet"
}
xpath is always a UBL path. On a CII invoice, look for the
matching CII field instead.