Showing the last 12 months based on a date slicer

When working with financial and sales data, clients often ask for charts showing the last 12 months of data.  This is actually very simple using relative date filtering.

In addition, they might ask to compare to the same month last year.  With a simple DAX calculation (SAMEPERIODLASTYEAR) it is possible to add this measure.

Here is the formula:

Same Month Last Year = CALCULATE(Sum(Sales[SalesAmount]),SAMEPERIODLASTYEAR('Date'[Datekey]))

For many users this is all they need.  The chart will update each month and they will always be able to see the last 12 months.  

However, this chart will not work with date slicers.  If the client adds a date slicer to the page and selects just one month, the chart will be limited to one month.

The reason the chart is limited to one month is because the date dimension relates to the sales fact table and it filters the data for the selected month.

However, this is not what the users want.  They would prefer to see rolling 12 months based on the selected month like below.

Configuring the data model for user selected rolling 12 month reporting

Step 1: Create two tables, Table 1 is Year and Table 2 is Month.  These tables will not relate to any of the other tables in the data model.

           

a.     From the Home Ribbon chose Enter Data

b.     Create a Year table with one column (Year)

c.     Create a Month table with two columns (Month #, Month)  (Month # can be used to sort the month names in the proper order)

Step 2: Create two new measures: Current Month Sales and Same Month Last Year Sales

Current Month Sales1 =

var Ldate = date(max('Year'[Year]),max('Month'[Month #]),1) //Last date

var Fdate = EDATE(Ldate,-11) //First date

var SumSales = Sum(Sales[SalesAmount]) //Calculation

return

 if(min('Date'[Datekey])<fdate,

         blank(),

         if(min('Date'[Datekey])>Ldate,

                   blank(),

                   SumSales))

Same Month Last Year Sales1 =

var Ldate = date(max('Year'[Year]),max('Month'[Month #]),1) //Last date

var Fdate = EDATE(Ldate,-11) //First date

var SumSales = CALCULATE(Sum(Sales[SalesAmount]), Sameperiodlastyear('Date'[Datekey])) //Calculation

return

 if(min('Date'[Datekey])<fdate,

         blank(),

         if(min('Date'[Datekey])>Ldate,

                   blank(),

                   SumSales))

Step 3: Create a chart using the two new measures with an axis for the month from the date dimension.  Add two slicers on the report from the Year and Month tables created in the step 1.

Summary

This approach can be used with an entire report as well.  Simply create additional measures as needed.  In addition if you would prefer six months or three months, then simply update the formula by replacing -11 with -5 or -2.