Have you tried editing the query in the Advanced Editor. I posted a similar solution here http://community.powerbi.com/t5/Desktop/Power-Query-M-filter-data-by-Dynamic-Date-PQ-not-DAX-Start-of/m-p/55693#M22623
Have you tried editing the query in the Advanced Editor. I posted a similar solution here http://community.powerbi.com/t5/Desktop/Power-Query-M-filter-data-by-Dynamic-Date-PQ-not-DAX-Start-of/m-p/55693#M22623