I don't have a history book handy, but the "dark ages" is the time preceeding the medieval period. This might be roughly between 500- 1000 AD depending on your point of view.
I'm a big fan of the medieval period, especially towards the end of that era nearing the Reniasssance. To me, "armor" must have four feet - being on a horse. I like the pagentry of the period and the opportunity to paint heraldry and intricate brocades. Also, many fantasy figures borrow heavily from the medieval period.
That said, I enjoy other periods, for example: Reniassance, Zulu Wars, American West, WWI, and "between the wars"(WWI and WWII). I even have done a Napoleonic or two! To me, painting a figure is a way of time travel - I can experience the era, if only in my mind. So, I'm open to new experiences and interests.