Here's a game you can play at home: keep your actual date of birth but project your life from there backwards instead of forwards, thinking how you'd have been affected by the different background. It's surprising how close history is to your life, at least if you're old.
I was born between the Sputniks, so in the backwards line I get post-war austerity instead of 60s psychedelic rebellion. Instead of being the capitalist prodigy selling sweets to my little mates for horrendous mark-ups, I need ration coupons for them, as my older brother did (though as he was an only-grandchild at the time he always ended up with our grandfather's sweet ration too).
At 12 I stayed up late to watch the Moon landings, but in the reverse line 1969 becomes 1945 and the technological triumph of the West becomes Hiroshima. Apollo's "We came in peace for all mankind", meaning "We've won a major victory for our side in the Cold War" becomes Truman's "Shortening the war saves Japanese lives too", meaning "We must show the Russians the Bomb before the armies of democracy melt away and leave the gigantic Soviet military dominating the world." I'd probably have missed much of the moral subtlety, but can't imagine getting the same fundamental optimism and scientific faith from the mushroom cloud as I did from the space race.
At 18 I went to university for maths, though got sidetracked by history and computers, events which fall in 1939 on the other path. It would be nice to think that these interests and talents would have got me into Bletchley Park to invent the modern computer, but probably not. It was already a very different world, with Turing suffering fatally from homosexuality being illegal and much frowned upon, no women in the core team (and Cambridge not awarding them degrees yet), television only for the very rich, and mobile 'phones rare even in science fiction. They wouldn't have wanted a working class lad from the Valleys, so I'd have been either called up or down the pit already.
In the late 80s came Thatcher's deregulation of financial markets in London's Big Bang, which sucked in most local programmers including me. It was a time of easy profit, incomprehensible financial engineering, unwise credit expansion and the always predictable, yet strangely surprising, Black Monday of 1987. In the reverse line it's 1929, the Wall Street Crash and the Great Depression. In that world without computers, but with the same need for numeracy and game playing that all markets thrive on, perhaps I'd have still been something in the city, helping to keep the boom and bust cycle going round again.
Into the 90s and I'm at the high point of my technical career, pushing computer emulation to alarmingly weird levels and making up new languages in which to think new things. In the alternate world it's the early 20s, bizarre language is the realm of Eliot and Joyce, for humans rather than machines, and technological innovation is heading for the tank and aircraft war of the future, but only in Germany and Japan, largely ignored in Britain and France as they plan to refight the last war again. Would I have been a poet writing gibberish or the military strategist who saved the world? Hard to say.
In the late 90s I move fully into management, overtaking the middle-class public school educated lads to recruit and lead them. Back in 1917 perhaps that would have had me penetrating the English officer class to lead men to certain death. But then I'd have to manage that curious mixture of incredible physical courage and complete unwillingness to rebel against commands for largely useless tactical sacrifice within a largely useless war. Whereas there's some argument that the second world war was needed to stop bad people doing evil, there's no such case for the first one, just a mixture of accident and competition for resources. I'd like to think I'd have been brave enough to take the disgrace and prison of conscientious objection rather than join in making it worse. But women and white feathers: very difficult.
Then there's the question of my grandfather, as a possible glimpse of me two generations earlier. He left school at 13 to go and make steel, harder work than I've ever done, and had one shelf of books, which was exceptional then. I suspect he was at least as clever as me, but lacking the breaks had to make his own opportunities. So he ran the village gambling rackets, raising money for old people long before the Welfare State. He organised carnivals back when communities would co-operate in such things. He managed a singing group and took them on the hunger march to London to entertain miners in the General Strike. No-one put him in charge of things, he just did it, as I've frequently done in games but not so much in real life lately: maybe such things were easier in a less regimented time.
More recently, in our timeline a tsunami devastates the Indian Ocean coastline and everyone knows in minutes. In 1908 in Siberia the Tunguska impact blasted everything flat for hundreds of square miles and, although the sound of it was detected in Britain four hours later (it was a big bang) the scale of it only became apparent when outsiders trekked in years later. Perhaps they speculated on what would have happened if the thing had landed on a city, or even in the North Sea. Tsunamis there would swamp Holland and East Anglia at point blank range, and maybe swell very high as they narrow through the Skaggerak or sweep directly over low-lying Jutland. The wreck of imperial homelands might ease their colonial grip, and if they had to work together on rebuilding rather than arms racing their dreadnought fleets into 1914, perhaps the Mud of Flanders would now be a symbol of recovery, rather than of man-made catastrophe.
2012 and 1901, London Olympics (without rationing the athletes' food as in 1948) and Victoria's Jubilee. A queen who has reigned since the middle of the previous century bringing history into the present, a superpower which fights in Afghanistan, Iraq, and anywhere else British imperial interests are challenged, without yet questioning its right to world domination.
And the future, a time of massive technological, economic and social advance, of civil war in the US, of scientific understanding turned upside down again and again, of conflict of rich and poor between and within countries - yes, welcome to the 19th century.