In Your Edit Calculation, If you would Blend using Date, the Data will be limited to June 18 only.
But You can Try This
IF ATTR(month(Date))=ATTR(month(Date1)) Then "T" ELSE"F" END
Drag to Filter and Select "T"
If this Does Not work, Please create a simple example in a packaged workbook and attach for faster results.
This was my first approach deepak..
I realized interval filter data is year-month
Sheet2 data has yy-mm-dd from datasource..
So as of now my hands are tied with this blunder mismatch
Interval is a field in source 1 with year-month as data
COMMS_DATE is a field in source2 which is yy-mm-dd
Add 01 for date and create a new date, Use Datetrunc to bring data to 6/1/2018 across June
Actually this should return 6
MONTH(Datetrunc,'month',MAKEDATE(your Year, Your Month,01))
and then you have other date
MONTH(Datetrunc('month', Your second date))
Both will give you 6
Then you can do