What standard do language codes of the form “zh-Hans” belong to?

The current reference for identifying languages is IETF BCP 47, which combines IETF RFC 5646 and RFC 4647. Codes of the form ll-Xxxx combine an ISO 639-1 language code (two letters) and an ISO 15924 script code (four letters). BCP 47 recommends that language codes be written in lower case and that script codes be written “lowercase with the initial letter capitalized”, but … Read more