Position of שיר של יום

When did Minhag Ashkenaz switch to saying Shir shel Yaum after Ŋoleinu? In the Divrei Kehillaus, R' Geiger brings that it was customary to say שש"י before Adaun Ŋaulom in Shacharis and at Breuer's, it is said after kaddish shalem of Shacharis. Why was this done?