Month of year Api for Driver Implementation

We are facing relative date-formatting issues in cubejs metabase driver implementation. (Rest API driven)

Prerequisite: download cubejs driver from github release

Use Case. Let say I have field dateordered. I select "orderfacts" table - open in query builder, group by dateordered then select Month of year. Error "month-of-year granularity not supported by Cube.js".

The Question: ATM we can't find way how to convert datefield to relative date formats in metabase driver.
(postgres can do this by "commands" Mon, NM, dy, DD, WW...etc. ).

We are looking for example code, how to improve the cubejs driver or API doc for handling relative date in driver. (convert/inherit relative dates from a simpe datetime field.) - avoid generate unnecessary fake dimensions.

many thanks