Thanks for your prompt response.
I found that the expression works fine when I am selecting date. The problem occurs when I am selecting Month-Year. It shows data for that month only. My requirement is to get the data from QUARTER Start till date. Eg. if i am selecting Apr-2016, It should give me the data for date range 1st April 2016-30th April 2016.
May-2016 should display the data for the range 1st April 2016-31st May 2016.
I am using a drill down group Month-Year--> Transaction Date.