I have attempted to place each event into a general category to make it a bit easier. Let me know if I have missed any alternatives or have got my categories completely wrong.
ENGINEERING - inventions, construction.
MILITARY - battles etc.
GOVERNMENT - anything involving how the country is run, including monarchs
LAW - A broad category covering any acts or decisions made by parliament or other authorities
CULTURE - important cultural works
SOCIETY - changes in society, including important immigrations and human rights events
SCIENCE - important events from any branch of science