wasn't a great day for Julius Caesar. The ides (15th) of each month was a festival honoring Flamen Dialis the high priestess of Jupiter. Julius Caesar was warned by a seer to beware of the ides of March. He scoffed at the idea. He was assassinated on 3/15/44 BC at a meeting of the senate. His best friend Brutus led a group of conspirators numbering 60 who killed Caesar. A little bit of over kill having 60 people stabbing away.
Four years later on the anniversary of Julius's assassination Octavian (later know as Augustus) executed 300 senators and knights. Octavian was Caesar's adopted heir. He considered this a sacrifice at the new altar in memory of Julius. These people took and eye for an eye very seriously. So now you know the rest of the story.