The end of WWII was not a single day or moment, because the countries of the Axis in each theater surrendered at different times. 

V-E day

After a long hard war, Germany finally capitulated, ending WWII in Europe

V-J Day

After years of drawn out guerilla warfare, Japan was finally laid low by the detonation of the worlds most devastating weapon ever deployed in combat.  


"Little Boy" Was dropped on Hiroshima August 6, 1945
"Fat Man" Was dropped on Nagasaki August 9, 1945

"I know not with what weapons World War III will be fought, but World War IV will be fought with sticks and stones." 
-Albert Einstein