ISO 2711 is a standard superseded by ISO 8601^[1]. Identification of days by ordinal dates was originally defined in ISO 2711. ISO 8601, Data elements and interchange formats – Information interchange – Representation of dates and times is an international standard for date and time representations. ...

References

1. ^ Technical Committee ISO/TC 154, Processes, data elements and documents in commerce, industry and administration. (2004-12-01). ISO 8601:2004(E). ISO. Retrieved on 2006-11-15. “Annex A … Identification of a particular date by means of ordinal dates (ISO 2711) and by means of the week numbering system (ISO 2015) were alternative methods that the basic concept of this International Standard could also encompass; thus, ISO 2015 and ISO 2711 have now been superseded.”