When creating a dataflow with columns which are date (only) and time (only) data types a warning message appears in the bottom right of the dataflow stating:
The query "" contains columns with complex types that cannot be loaded.
The query will save and refresh but if used as a datasource in Power BI Desktop, the data type for the date (only) and time (only) columns will get reset to a datetime data type.
The same issue has been reported before internally: CRI 94252427. This is by design currently. For more information, please see @nimrodg 's post here:
Best Regards,Qiuyun Yu