Android: SQLite Getting all records that inserted in last 7 days

Cursor cursor = db.rawQuery("SELECT * FROM expenses WHERE expense_date > (SELECT DATE('now', '-7 day'));", null);

I have this above query to get all records that inserted in last 7 days. But as a result of this query i am getting all the records. The date column of these records is inserted via Android's DatePicker and they are in 30-Jul-2015 format. I guess that's why this query does not work properly. Is there a way to make them consistent to get this query work properly or i am missing out something else ? Any help would be appreciated.