The '20s were the aftermath of the Great War. The world had seen nothing like it. For the first time battles were fought in the air, poison gas was used, and tanks made an appearance. Many women took mens jobs until the men returned from war. Women were on the battlefield as nurses. The '20s were roaring for a goodreason: Survivors of the war went crazy in celebrating life. For the first time in history (other than a high fever) women cut their hairshort, hemlines went way up. Clothing for women was far less contricting: no corsets and simple roll up stockings were worn. Women took up the 'outrageous' habits of smoking and drinking - and men accepted it. Women wearing cosmetics became fashionable. Class structures - on both sides of the Atlantic - brokedown. Women got the vote. It was a wild and happening time. Divorces were nowacceptable - even a little daring.
The '30s, by contrast, saw the stockmarket crash and a world wide depression. As usually happens in less affluent times, conservatism took over. Hemlines wentdown. The fun of the '20s was considered decadent. Divorce in the middle class was looked upon as irresponsible, but still acceptable in the upper classes.
When the '40s arrived the habit of women smoking, drinking, and gambling was no longer considered bold but a usual thing. A war was on - an even more advanced one than before, and again women took up male jobs and nursing on the front lines. Morals were a bit looser as one never knew how long one had to live. People lived for the moment.