If you want a realistic timeline, you need to first start with the end result. What is life like in this dystopian future? Are the residents of this world familiar with the timeline or only a select few? Is there democracy or dictatorship? Is there a caste system?
Once you have a good idea about what you want the world to be about, you rationalize in ways to explain why it turned out that way. If it is a dictatorship when did the dictator take over? Has it been like that for generations or did it happen recently? If the world is a democracy, what are some of its flaws and why does it have them? What caused the world to turn to democracy?
Now that you have a few questions, you should start being able to come up with answers. There should be many things that would have had to happen for this to be the case. What people/groups were involved in the event? Were there any heroes/villains in the event? Where are they now/What happened to them?
Sprinkle other events in with these that might follow in line with the mentality at the time. If two countries had a period of tension, then it would follow that there would have been moments similar to that of our own timeline such as during the cold war. You can use actual events like this as inspiration for similar things happening in your timeline. Were there any natural disasters? Any other noncircumstantial wars fought? Breakthrough technology that changed everything?
Your last step should be determining precise dates for these events. Keep them reasonable and make sure that these significant events in the timeline also make sense with other events in your timeline. For example a revolution didn't take place after the switch to democracy unless the democracy was a farce. For the sake of consistency, I would advise you to write down exact dates rather than general rules as you can refer to them later in your story. It also makes your timeline read much more like a history lesson like something happened.
Hope that helps!