Measure not working when selected multiple months

[AshP]

Hi, I created a below measure to calculate the previous month sales. It is working fine when I am selecting single month but not adding up when selecting multiple months. Eg. When selecting January, it is giving the right number but when I am selecting january and feb it is showing the latest month data but I need the sum. How can I fix this ?

Prevs_month =

 var curmon = Month(Max(calendar[date]))

 var curyer = year(max(calendar[date]))

 var prevmon = if( curmon = 1, 12, curmon-1)

 var preyer = if(curmon = 1,curyer-1,curyer)

 RETURN

  calculate(sum(table[sales]),

    Month('Calendar'[Date]) = prevmon,Year ('Calendar'[Date])= preyer)

[amitchandak]

@AshP , Try to use time intelligence functions

examples

MTD Sales = CALCULATE(SUM(Sales[Sales Amount]),DATESMTD('Date'[Date]))
last MTD Sales = CALCULATE(SUM(Sales[Sales Amount]),DATESMTD(dateadd('Date'[Date],-1,MONTH)))
last month Sales = CALCULATE(SUM(Sales[Sales Amount]),previousmonth('Date'[Date]))
MTD Sales = CALCULATE(SUM(Sales[Sales Amount]),DATESMTD('Date'[Date]))
last MTD Sales = CALCULATE(SUM(Sales[Sales Amount]),DATESMTD(dateadd('Date'[Date],-1,MONTH)))
last month Sales = CALCULATE(SUM(Sales[Sales Amount]),previousmonth('Date'[Date]))
next month Sales = CALCULATE(SUM(Sales[Sales Amount]),nextmonth('Date'[Date]))
this month = CALCULATE(SUM(Sales[Sales Amount]),DATESMTD(ENDOFMONTH('Date'[Date])))
last MTD (complete) Sales = CALCULATE(SUM(Sales[Sales Amount]),DATESMTD(ENDOFMONTH(dateadd('Date'[Date],-1,MONTH))))

Power BI — Month on Month with or Without Time Intelligence
https://medium.com/@amitchandak.1978/power-bi-mtd-questions-time-intelligence-3-5-64b0b4a4090e
https://www.youtube.com/watch?v=6LUBbvcxtKA

[AshP]

The same problem with time intelligence functions, They are working fine for individual months. But not working when selected more than 1 month.