Attrition Dashboard - Tenure wise

hi, karlosdsouza 

First, you should know that calculated column and calculate table can't be affected by any slicer. you could create a measure instead of column.
Notice:
1. Calculation column/table not support dynamic changed based on filter or slicer.
2. Measure can be affected by filter/slicer, so you can use it to get dynamic summary result.
here is reference:
https://community.powerbi.com/t5/Desktop/Different-between-calculated-column-and-measure-Using-SUM/t...
https://www.sqlbi.com/articles/calculated-columns-and-measures-in-dax/

Second, try this way as below:

Step1:

Add a date table as a slicer

Step2:

Use this formula to create a 

Measure = 
VAR _tenure =
    IF (
        SELECTEDVALUE ( Table1[Status] ) = "Active",
        CALCULATE (
            SUMX ( Table1, CALCULATE ( ( MAXX('Date',SELECTEDVALUE('Date'[Date],NOW())) - SUM ( Table1[joining date] ) ) / 30 ) )
        ),
        CALCULATE (
            SUMX (
                Table1,
                CALCULATE (
                    ( SUM ( Table1[leaving date] ) - SUM ( Table1[joining date] ) ) / 30
                )
            )
        )
    )
RETURN
    _tenure

Step3:

Create a group table

Step4:

Use these formulae to create the result measure

HC = var _table=FILTER(GENERATE(table1,table2),[Measure]>Table2[Start]&&[Measure]<=Table2[End]) return
COUNTAX(_table,[Kind])+0

Attrition = var _table=FILTER(GENERATE(table1,table2),[Measure]>Table2[Start]&&[Measure]<=Table2[End]) return
COUNTAX(FILTER(_table,[Status]="Left"),Table2[Kind])+0

Result:

Note: you could use date field as a slicer or create other fields eg. year-month in date table then use it as a slicer.

And here is pbix file, please try it.

Best Regards,
Lin