Sculpture of Augustus
Augustus, born Gaius Octavius Thurinus, was adopted by his great-uncle Julius Caesar in 44 BC, and between then and 27 BC was officially named Gaius Julius Caesar. After 27 BC, he was named Gaius Julius Caesar Augustus. Because of the various names he bore, it is common to call him Octavius when refering to events between 63 and 44 BC, Octavian (or Octavianus) when refering to events between 44 and 27 BC, and Augustus when refering to events after 27 BC.
P. V. N. Myers A General History for Colleges and High Schools (Boston, MA: Ginn & Company, 1896)