Date Formats in EN 16931
Stop guessing format codes. 99% of valid Factur-X/ZUGFeRD dates use format 102 (YYYYMMDD).
Rule #1 The Format "102"
In the XML standard (CII or UBL), dates are almost always accompanied by a format code.
The standard EN 16931 strictly mandates format 102 which implies
YYYYMMDD.
<ram:OccurrenceDateTime>
<udt:DateTimeString format="102">20260218</udt:DateTimeString>
</ram:OccurrenceDateTime>Critical Date Fields
Invoice Issue Date
Validation Date. The exchange rate is calculated based on this date.
Due Date
When the payment is expected. Optional if using payment terms description.
Actual Delivery Date
Date of supply of goods or services. Vital for VAT tax point.
Using the API
When using React/Node.js/Python with Factur-X Engine, you don't need to obscure XML nodes. Just pass an ISO-8601 string in the JSON metadata, and we convert it to format 102 automatically.
// JSON Metadata Payload
{
"date": "2026-02-18", // We convert this -> 20260218 (102)
"due_date": "2026-03-31", // We convert this -> 20260331 (102)
"delivery_date": "2026-02-17"
}Still getting formatting errors?
Use our validator to verify if your date format codes match the strict EN 16931 Schematron rules.