Building on my comments from Thursday - one of the biggest problems creators may face when constructing a timeline out of whole cloth, rather than letting it evolve naturally, is that will is not the only thing that determines how history unfolds. Sure, I'll grant that there are plenty of things that don't happen because people in positions of power don't want them to happen, but on the other side of the equation, things won't happen with no other motivation than people wanting them to.
Space exploration timelines, in particular, tend to get clobbered by this. While there are plenty of people who really want things to happen in space, that desire is not enough to overcome the massive expense of launch. Sure, things are changing, but not as quickly as many people probably would have liked. Take the last eight years - from 2002 to 2010, SpaceX went from being a new-minted startup backed by Elon Musk's internet money to the first private enterprise to launch its own spaceship. That's a great accomplishment in itself, but some timelines might have had SpaceX building O'Neill cylinder colonies by now - the optimistic mind doesn't have to worry about how the bills are paid. The big dreams of those who designed space colonies and cities in Luna were, in the end, ineffective rocket fuel.
Everything has a reason for happening, reasons that tend to reach well back into history. By contrast, it's easy for timeline writers to fall into the trap of acting as if there's no history to worry about - that the future is freestanding and self-supporting. But everything has a foundation.
For an example, I'll provide one of my old timelines, last modified on December 10, 2001. I have no idea where I was planning on taking it - I'd guess 2001!Andrew was planning on some kind of space-operatic setting - but I do know I was creating it in a vacuum, without any support. My suggestion: mocking of the timeline may be made easy and enjoyable by adding "For some reason." to the end of each entry.
Stern Seagull is not especially pleased by it.
2002 - George W. Bush assassinated, Dick Cheney ascends the Presidency. US warplanes begin bombing Somalia.
2003 - An attempt on the part of terrorists to release smallpox fails.
2006 - Chinese taikonauts orbit Earth.
2009 - Kim Chong-Il, longtime dictator of North Korea, is assassinated by revolutionaries along with most of his government. In the resultant chaos, Chinese forces sweep across the Yalu and install a puppet regime in Pyongyang.
2010 - Regional tensions inflame into the Final Indo-Pakistani War. The world is brought once again to the brink of nuclear annihilation as eighty-eight warheads scorch the Indian subcontinent with atomic fire and kill a billion people.
2011 - German is declared to be the official operant language of the European Union.
2013 - Quebec seperates from Canada.
2018 - European Space Agency establishes launch center at Nairobi.
2026 - After an eighteen-month journey, three internationally-crewed vessels arrive in orbit of Mars. Cosmonaut Alexei Voroshov is the first human to set foot on the Red Planet.
2028 - Alberta and British Columbia admitted to the Union as the fifty-first and fifty-second states.
2031 - Vietnam becomes a dependency of China.
2035 - Building off initial NASA research discarded from lack of funds, Chinese scientists build the Earth's first example of a functioning ion drive (quai fei).
2042 - In a demonstration of the sheer velocity provided by the quai fei drive, a Chinese vessel arrives at Mars after a journey of three months.
2047 - Development of practical nuclear fusion reactor.