Both are more notation frameworks than actual calendars, but only certain calendar designs are compatible with the framework and in some instances, out of several possible alternatives, a single one had to be chosen to be supported. Disclaimer: The use of the term “ISO” in the body of this article is not meant to claim or imply any formal approval or recommendation of proposals presented herein by the International Organization for Standardization (ISO). It is meant simply to signify that the proposals are compatible with ISO 8601.