Many fantasy authors pay more attention to developing cultures than geography, and while the geography of a fictional world is often more important than we give credit, this is not entirely a bad thing. After all, relatively few people are going to notice if your rivers are going in the wrong directions, or if the land to water ratio of your world wouldn’t actually support life. On the other hand, shotguns in a culture that has barely mastered the making of glass are going to be fairly noticeable. When working on your world remember that creating the illusion of reality is more important than mirroring reality itself. There are a lot of things that you could do wrong (for instance putting a jungle plant in the desert) that won’t break most people out of the story. Of course, this doesn’t mean that you shouldn’t pay attention, do your research, or trust people’s ignorance to cover your egregious errors, but it does mean that a rich, believable culture is going to be more important to most readers than accurate geography.
That being said, timelines can be a useful tool for the development of your world. However, this doesn’t mean that a detailed timeline is necessary. Tolkien’s timeline, The Silmarillion, is massively extensive (it’s a book after-all). On the other hand, some authors (Glen Cook for example), seem to have only a general idea of the history of their world that develops as they write. Let me say here that Tolkien and Cook are two of my favorite authors, and (while I’m not privy to Cook’s writing notes) appear to have two completely different approaches to background writing.
Whenever you’re writing a new world a basic timeline is a must. However, a basic timeline only requires a general idea of what’s happened. For instance, a basic timeline might be as simple as:
1-2500: Origins of the World
2501-4300: The Age of Fire
4301-5250: The Martian Rule
5251-9000: The Age of Chaos
9001-14000: The Rise of Man
14001-14653: The Rule of Empires
This basic timeline gives you a basic record of what has happened and how the history of the world has progressed. Each broad span of time is tagged with a title that will remind you of the general idea you had for that era. These eras can be filled in as necessary. For instance, if the first 60,000,000 years of your world is the collapse of gasses into a planetoid and the development of an atmosphere… well, you probably don’t need to fill in that era. Similarly, if for the next 30,000 years the world was ruled by jello people who built everything out of gelatin and left no discernible trace of their existence, you probably don’t need to fill in that era either. However, remember that worlds develop over time. The foundations of one culture can often affect the development of the next, and all those strange ruins you’re heroes love to explore had to come from somewhere.
How detailed your timeline is depends on a few of factors. 1) How much affect the era has on the history of your world: if your looking at an era that happened in the ancient history, you probably don’t need a year by year timeline, perhaps not even a century by century timeline. 2) How long the history of your world is: if your world is six billion years old your probably going to be looking at a lot of empty space in your time-line. On the other hand, if you world is only forty-five days old, you probably don’t want any blank spaced. 3) How serious your world is: the style of writing you do can have a large effect on the need for a detailed timeline. Stories that are intended to be comedic or tongue in cheek in nature generally have a lot more leeway for mistakes than stories that are very serious. This doesn’t mean that a detailed timeline won’t help your story (it always will), but you can get away with a lot more in comedy than in tragedy.
This certainly isn’t the last thing I’ll write about background writing, and probably not the last thing I’ll write about timelines, but I’ve learned better than to make promises about what’s coming next week. For now, work on your basic timeline, and then fill things in as needed.