I find it dated, but not to the 20s, the Shirleys I know are 40 to 50 years old. Also,
Shirley is a region of the town where I live. It doesn't have the best reputation, so that puts me off more than the datedness or the sound.
Also it makes me think of the scenes from the film 'Airplane' which went something like this:
"Surely you can't be serious?!"
"I am serious... and stop calling me
Shirley!"