Date Logic (auto incrementing year when arithmetic applied to month)

I’ve read the basic date variable documentation for using :MONTH :YEAR or having simple arithmetic applied to :MONTH+1 for example.

However, what happens if :MONTH+X equals a date next year, e.g.

Today is September 30, 2020. Send an invoice out with meta data in a description / product line / custom field that would describe to the end client that they are paying for a product for the next two quarters. I.e. October 2020 through March 2021.

Product End Date = (:MONTH+6 :YEAR) will not yield (March 2021), instead it would increment month by six but not account that year should be incremented.

Is there notation to include logical tests, like if/else? Else, how can we think about this? Is this use-case supported?

This is a limitation of the current design, we plan to solve this in v5