Indexes and date field on massive table

[K. Wolfe]

So I'll be creating a clustered index on a massive table (cust_id, action_date). My primary goal will be to keep a query such as this running at its best:

select
*
from
tbl
where
concat(month(action_date), year(action_date) = 112

Should I maybe think about creating a column with MMYY in it and index that?