Lets look at Nostradamus as some kind of reporter who writes about main events that happen in the future using his own style and words. This thought leads us to a few useful questions:
The number of events that Nostradamus suposedly reports on is impressive, and it would be far too much work for one reporter to witness all personally. The locations of the mayor events are far apart and some occured suddenly without prior warning. If Nostradamus was a reporter on contemporary events he could not have done any better, in his time information reporting was not as developed as nowadays, with television, radio and profesional news reporting. So how can we explain Nostradamus managing to collect all this information.
Reporters collect and compile information from a number of sources. They put together this information and describe the events in their own words.
You need to find and access a media (you need to know how to) before you can learn about an event. As a fact, you do not need to search long to find a summary of all great events of past centuries, it is probably all located in one volume, one video, one tape etc. Film, television and video are currently popular media to see past events. Each media has its own requirements to access it.
In order to write about events you must either be there (by coincidence - maybe) or you must have access to a medium containing information about the event, after the event took place.
There is no need to travel, no need to go back in time, just sit back, relax and watch and absorb that film. If you cannot see the film, you could still listen to the commentary and discription, it might give you the same knowledge. The point I am trying to make here is this:
A film that gives a summary about history would certainly explain how apparently an enormous amount of research could have been skipped and how all that valuable information could have been available as something that only needs to be looked at or listened to. It would give you knowledge about all mayor events of humanity right from the beginning of its existence. In our time and age we already possess the technology to make such summaries and are capable to record them to a variety of media. However we can not explain how such a summary would ever have been accessible to someone in the past.
Predicting the future might be hard, describing the past however is easy.
Could Nostradamus have been some kind of reporter, reporting news that happen in a future world