How to aggregate measure data to a particular position on Calendar

Hi,

How to aggregate data for given calendar to a particular date value.

I am have measure which have value like below:

DAY,CSKU,MKRT,VDC,Qty
20150409,prod123,ab,ab123,27
20150410,prod123,ab,ab123,47
20150413,prod123,ab,ab123,17
20150414,prod123,ab,ab123,34
20150415,prod123,ab,ab123,31
20150416,prod123,ab,ab123,41

I have created another Measure which will do the tssum for given start and end range.

DAY,CSKU,MKRT,VDC,Qty
20150409,prod123,ab,ab123,74
20150410,prod123,ab,ab123,74
20150411,prod123,ab,ab123,74
20150412,prod123,ab,ab123,74
20150413,prod123,ab,ab123,74
20150414,prod123,ab,ab123,74
20150415,prod123,ab,ab123,74

Now I need to pickup the data for date 20150409 and  I need to have date as 20150406