For that matter, Archduke Ferdinand's assination could be considered the start of it. So what cause that? The terrorists in Croatia could be a start.
How about the 'Treaty of Versailles'?
That started The War To End All Wars. It had an "official" ending on 11:11 11/11/1911 (as is shown by seismic records.)
Somebody named Archie Duke was shot by an ostrich.
You could just as easily argue that the French started it in 1871 when they declared war on Prussia that led to the Franco-Prussian War. The devestating loss the French suffered after that war led directly to WW I which led directly to WW II.