Which non fiction genre involves true accounts of only past periods or events

Historical non-fiction.

The non-fiction genre that involves true accounts of only past periods or events is called "Historical non-fiction." This genre focuses on documenting and analyzing historical events, periods, or individuals using factual evidence and research. Historical non-fiction books often provide insights into specific eras, wars, biographies, or cultural movements. They aim to inform readers about significant events and shed light on the impact of history on society.