1929: The horrors of the Great War are unprecedented in world history, leaving a generation disillusioned and cynical.

Today: After the vast international scope of World War II and the televised mayhem of Vietnam, politicians are only likely to commit to wars that can be waged with computers and longdistance missiles.

1929: The stock market crash of October 29 plunges the United States into the Great Depression, and other world economies soon follow.

Today: Because of advances in travel and communications, the economies of separate nations are more dependent on each other than ever before.

1920s: Modernism, the artistic movement that turns away from traditional forms, brings thrilling new possibilities to painting, literature, and music.

Today: After post-modernism, which reflected art's awareness of its own techniques, artistic theories have become divided so that no particular school dominates artistic thought today.

1929: "Feminism" is seen as a rare, exotic...