Complex sentence: Finally, the decision was made in On September 27,1981, the station switched to an all-talk format: at 6pm on that date Justin Clark played the last song, "American Pie" by Don McLean.
Split into simpler sentences: Finally, the decision was made in September of 1981 to drop music and switch to an all-talk format. The switch was made on the 27th of that month at 6pm, with Justin Clark playing the last song, "American Pie" by Don McLean.