Wouldnt that be 1880 when they became fully trinitarian not 1990?
When Barnhouse and Martin studied the SDA in the 50s and they were amazed to find Arian teaching and also trinitarian literature all with the church logo on it. Barnhouse and martin presented this material to Scolars from the general conference and even they were a little taken aback and didnt beleive how it had happened. Of course SDAs in the past have had no clear teaching have had differing positions .