Hi Pallavi,
If you need to only display your data as hierarchy at report level. note that such functionality is only available with OLAP data with hierarchies.
In your case you need to play with formatting of a table to make it look like a hierarchy.
Please refere following link for more details.http://scn.sap.com/community/businessobjects-web-intelligence/blog/2013/06/05/bobj-trick-to-display-table-data-in-hierarchy-format
But If you need to use only power of drilling functions then go for custom hierarchies/custom navigation paths as suggested by others in above comments.
Note: Custom Navigations path does not display day in hierarchy form but allows you to navigate through hierarchy using drilling options.