​In many cases, data that are exchanged in SDMX data messages do not relate to the calendar year. However, many statistical system implementations require that data are mapped to and stored as the real calendar. The document "Guidelines on Non-Calendar Year Reporting of Data" (Version 1.0, November 2016) provides recommendations for four use cases of such non-calendar year data: a) Reporting year is equal to the calendar year; b) Reporting year starts on the first day of a month different to January; c) Reporting year starts on a given day in the year, and d) Reporting year ends on a given day in the year.