I would like to share some knowledge from my experience working with cube datasource in tableau.
Working with cube datasource in tableau will have very limited features. We can't create aggregate calculations on tableau as the multidimensional cube is already aggregated data source.
I prefer you to go for secondary data source containing dates and do join with the cube datasource. Ex secondary datasource will have two columns date string and date value (Date string: 2017.FEB Date value: 01-02-2017)
To create calculations we should create a calculated member using MDX queries.
Good luck with your analysis!
thank you for your response, but a secondary datasource is not an option, unfortunately.