Of course, the first ever recorded Olympic Games was in 776 B.C. but the games were banned in 393 A.D. So, April 6th, 1896 was the date that the first modern Olympic Games was held:
The Olympic Games, a long-lost tradition of ancient Greece, are reborn in Athens 1,500 years after being banned by Roman Emperor Theodosius I. At the opening of the Athens Games, King Georgios I of Greece and a crowd of 60,000 spectators welcomed athletes from 13 nations to the international competition.
You can read more about these first modern Olympic Games at http://www.history.com/this-day-in-history/first-modern-olympic-games and you can check out our books on the Olympics!