How about first having the industrial era which encompass the "
http://en.wikipedia.org/wiki/Industrial_revolution" (roughly from 1780's to 1850) and then have an other era, Imperial age, which represents the "
http://en.wikipedia.org/wiki/Second_Industrial_Revolution" and the "
http://en.wikipedia.org/wiki/Imperialism#Age_of_Imperialism".
You know with the scramble for Africa, the rise of Japan and incursions into China.
WWI could be classed as a colonial war, all the major combatents was either empires or had colonies. And both sides of the war wanted to expand theirs colonial empires, at the cost of the other side.
The imperial age could run all through to the end of WWII(and further still as many European nations had colonies well after that).
The "modern era" could start at around the 1960's encompass the economic boom of the time, the space race, mass consumerism, mass transit, the counter culture... etc.
Edit: sorry for lousy linking, writing on a MacBook, and apparently im not a "MacPerson"