Here is a rough timeline for the duchy of Braunschweig
and following is a link to the historical development in Germany at various time frames.
A good source for local history timelines can be found in village chronicles. These are taking historical developments of specific areas into account, and let the researcher have a glimpse of ancestors' lives from various points of view. Ortschroniken can usually be retrieved through a mayor's office or historical societies. A Google search may assist with availability.