1815: The world's political powers are in a state of change. The French army of Napoleon Bonaparte is defeated by the British at Waterloo, ending his dominance of Europe, while the British army is defeated in the Battle of New Orleans, establishing America's control of the continent.

Today: The major military powers seldom come into direct conflict with each other, although they do take sides in the conflicts of smaller nations.

1815: A woman in mourning for a dead relative is expected to wear black for at least a year and to stay out of public social situations for at least that long.

Today: Social conventions for how a person should express her or his grief have less stringent rules.

1815: A London banker is able to get news of Napoleon's defeat days before the newspapers have the information because he has associates send the report by...