For instance, some historians talk about the "long nineteenth century" which is defined as running from the French Revolution in 1789 through the start of World War One in 1914, a 125 year "century".
Brin, however, has his own breakdown:
The last two centuries (and possibly more) didn’t “start” at their official point, the turning of a calendar from 00 to 01. That wasn’t when they began in essence, nor when they first bent the arc of history.I think this is rather off. The peace of 1814 to 1914 was an uneasy one, the same technological and cultural developments that Brin cites as causing such optimism in 1913 also caused incredible uncertainty and upheaval.
No. Each century effectively began in its 14th year.
Think about it. The first decade of the 20th century was filled with hope and a kind of can-do optimism that was never seen again -- not after the horrific events of 1914 shattered any vision that a new and better age would arrive without pain. Yet until almost the start of World War I, 19th-century progress seemed unstoppable and ever-accelerating.
Consider the world of 1913, when regular middle-class folks in the U.S., U.K., France, Germany and so on were acquiring unexpected wonders: clothes-washing machines, gas stoves, gas and then electric lighting, indoor plumbing, refrigeration, vaccinations, telephones, radios, motor cars. Stepping outside you would see and hear human beings flying through the sky -- with a looming confidence that soon you would get a chance to join them.
Yes, all of those techno-advances continued after World War I. Social changes such as women getting the vote were harbingers of more to come. But after 1914, the naivete was gone. People realized that the 20th century would be one of harsh struggle accompanying every step of advancement. And along the way to hard-won better times, the age would spiral downward first, into the deepest pit that humanity ever knew, before our parents (or grandparents) clawed their way out of the nadir of 1944 -- the focal year of a century that truly began in 1914.
All right, that’s just one data point. Is there another? Well, look at 1814, the beginning of the Congress of Vienna and the so-called Concert of Europe that made possible the continent’s longest extended period of overall peace, as the great powers turned from fighting bloody wars to perfecting their colonial empires. Those two years -- 1814 and 1914 –- each marked a dramatic shift in tone and theme (in the West, that is), so much so that they represented the real beginnings of the 19th and 20th centuries.
This is why I think it makes a lot more sense to see the 19th century, thematically, as beginning with the French Revolution in 1789, and the advent of mass war in the 25 years from 1789 to 1814. The following decades of the 19th century saw some attempts to roll back the political revolution of 1789, but political, cultural and technological revolution continued as theme throughout the century. Industrialization proceeded rapidly throughout Europe during the 19th century. In 1848, revolution swept Europe. Nationalism was increasingly stirring. The revolutions were mostly put down, but they had made gains and the order restored was more precarious. In the 1860s and 70s, the European continent was shocked by a series of short, sharp wars: The wars of Italian unification. The Franco-Prussian War and the Austro-Prussian war, which between them resulted in the formation of a unified German empire and its emergence as arguably the strongest power in continental Europe.
Meanwhile, industrialization was continuing apace. Socialist and labor political movements were becoming increasingly powerful. Turkey was coming apart as a great power, the Balkan countries were breaking off via a series of bloody wars of national liberation, and these Balkan powers (backed by Russia was was quickly becoming a major power as it industrialized) were putting pressure on the Hapsburg empire, which was also suffering from its own internal divisions.
In other words, while the 19th century was indeed a period of rapid development, it was also a period of uncertainty and unrest. Technology was moving forward by leaps and bounds. What would one day be called the "developed world" was developing, and in the process new fortunes made old poverty increasingly politically unacceptable.
I'd make the case for 1789 to 1914 as the "long 19th century" as a period of technological advancement, political and cultural revolution, and the emergence of a number of increasingly nationalistic great powers on the European scene, as countries came to be identified with the people (in the sense of race or cultural group) they represented rather than merely a set of elites ruling a given piece of territory.
The 20th century which emerged with sudden violence in 1914, I would characterize as being a period during which the great powers and major political ideologies struggled for dominance, with the eventual emergence during the second half of the 20th century of two superpowers: the USA and USSR.
Given that, I'd provisionally put the beginning of the "21st Century" in 1991, with the fall of the USSR and the emergence of the monopolar world with the USA as the lone superpower. If I'm right, the 21st century thus far seems to be characterized by a single major power maintaining a large enough monopoly on military force, while technological innovation has gone through another spurt of rapid development, and the global economy has become increasingly integrated.
Of course, even by that measure we're only 23 years into something like 100, so who's to say what the theme of the 21st century will look like in another 80 years.