The Star Wars Galaxies History can be divided in this fashion:
Ancient Pre Republic
Old Republic/Sith Pre-Ruusan
Old Republic/Sith Post-Ruusan
New Republic/Imperial Remnant
Galactic Alliance/Sith Empire/Imperial Empire
The books and comics go by the dating system using the Battle of Yavin as the reference date. The Prequel movies take place in Old Republic’s Post – Ruusan era. This is why some same the Republic is only a thousand years old: it was reorganized, as was the Jedi’s role, after the Sith were defeated at Ruusan. They end with the formation of the Empire. The Original Trilogy takes place in the Empire/Rebellion era.