June 28 (ie: today, meat head) is also the day Archduke Ferdinand of Serbia suffered a head-first collision with a bullet shot from the gun of Gevrilo Princip, setting into motion the chain of events that led to the outbreak of World War I.
If you ever went to a Jewish camp or a kiruv seminar you may have heard that this occurred on the 9th of Ab. If so (brace yourself) you were not told the truth. June 28, 1914 was 4 Tamuz. (Please don't throw down your head-gear and change into jeans on my account. I'm sure everything else you were told at camp or at the kiruv seminar was true.)
A more common lie is that WWI itself broke out on Tisha B'av. This is an especially nefarious lie because it's partially true. Germany did make a formal declaration of war on 9 Av. However, by that point, the war had, in point of fact, already "broken out." I quote from Yuter's authoritative essay on the lies people tell about Tisha Bav:
The first formal declaration of war came on July 28th when Austria-Hungary declared war on Serbia. Hebcal returns 5 Av. Russia mobilizes against Austria and on July 31 (8 Av), Germany gives Russia an ultimatum to either disarm or face war. Due to Russia's refusal, Germany formally declared war on Russia on Aug 1st. This was in fact 9 Av. The fighting began on Aug 2nd when Germany invaded Luxembourg, and Britain joined in on Aug 4th when Germany invaded Belgium.So the first declaration of war came on June 28th and fighting actually began on Aug 2nd. Neither one of which is 9 Av.Ah well.