When you say "specific to that current month" what do you mean? Are you equating QTD with "last 3 months"? Tableau has a lot of options when it comes to dates, and if you're willing to get your hands dirty using some date functions, you can pretty much do anything. Give us a more detailed description of what you're trying to do.
Create a parameter which can select your current year or date & according to that create a calculated field with the use of Case statement. For Previous Year you have to change the Parameter value in date in a calculated field & then use Dateadd function with the use of -1. If you will provide more detail or some sample data, i will more explain you that.