You might accomplish this by creating a false 0 value in the first week via a calculation. Similar to:
If [Date] < 7/1/2015
Else [Actual Values]
After you do this, it will likely still create null values for those time periods and drop them from the view. To fix this you'll have to go to Analysis<Table Layout and select "Show Empty Rows/Columns". The selection of rows or columns depends on what shelf your values are located.
Let me know if you have any problems with this or if it doesn't work for you. An example workbook is the fastest way to work through it.