FHIR-I is reviewing extensions against the data types (which we're responsible for) and we don't understand the purpose of the partialDateTime extension.  It says it's to convey partial dates, but the base data type already allows that (you can send YYYY, YYYY-MM, YYYY-MM-DD, or a full dateTime).  As well, all 4 components are mandatory, meaning you can't omit them.

In the examples, all components are populated with proper values, but no actual dateTime value is specified which is extremely bad practice.  You should always send a value along with the extensions if it's possible to do so as you should expect at least some recipients won't recognize the extensions.

Please either drop this extension or come to a FHIR-I call and explain what it's trying to do and we can work with you on how best to do it (and how to better describe it so that the usage is clear).

Same issue for Partial Date Time