Step 1 - Create a Parameter

1. Right-click anywhere in the Data pane of Tableau Desktop and select Create Parameter...
2. Fill in the different fields as described below: 
   1. Name: Calendar Type
   2. Data type: String
   3. Allowable values: List
   4. Manually add the following values: Calendar, Fiscal

Step 2 - Create three calculated fields

1. Select Analysis > Create Calculated Field...
2. Name the calculated field: Display Month
3. Enter the following formula and click OK: 

   DATENAME('month', [Order Date])

4. Select Analysis > Create Calculated Field...
5. Name the calculated field: Display Year
6. Enter the following formula and click OK: 

   CASE [Calendar Type]
     WHEN "Calendar" THEN DATENAME('year', [Order Date])
     WHEN "Fiscal" THEN "FY" + DATENAME('year', DATEADD('month', 6, [Order Date]))
   END

7. Select Analysis > Create Calculated Field...
8. Name the calculated field: Month Sort
9. Enter the following formula and click OK: 

   CASE [Calendar Type]
     WHEN "Calendar" THEN DATEPART('month', [Order Date])
     WHEN "Fiscal" THEN DATEPART('month', DATEADD('month', -6, [Order Date]))
   END

Step 3 - Build the view

1. Drag [Display Year] and [Display Month] on Columns
2. Drag Sales to Rows.
3. Right-click on [Display Month] and select Sort...
   1. Choose "By Field" and select [Month Sort]
   2. Choose "Minimum" aggregation
   3. Then click OK