sharepoint calculated column

Hi I have two columns in a sharepoint doc library one called Next Review Date another called Current Date which is a calculated column defaulting to the current date.  I want to have a third calculated column that shows Review Status with 5 possible text outcomes,  In Date, due in 3 months, Due in 2 months, due in 1 month or overdue.

How can I achieve this with a formula in a sharepoint calculated column?