prize17-5, Exercise 1: A simplified starting date

Model answer (check the details):

The Palomar night of 21 August 1935 is often named as the start of the swing era because a young crowd responded warmly to Goodman's band. It is a simplification because big bands had been developing for years before it (Chapters 3 and 4), because the audience was not equally warm at every tour stop, and because the label was added afterwards by writers looking back.

Two other factors that built the audience: radio broadcasts, which carried live band music into homes across the country, and dancing, since ballrooms and dance crazes created steady demand for bands with a strong beat. Records and jukeboxes also helped.

Care: a single date makes a good story but hides a slow build. Say "often described as the start" rather than "the start".