Anniversary-itis
A small part of the problem may lie with the 5-year carousel of anniversaries. The dropping of the atom bomb and the Battle of Britain are now being commemorated. Last year we commemorated D-Day. Next year we will remember the invasion of Russia, the sinking of the Bismark, and Pearl Harbour. The current historical preference for viewing the two World Wars as a single entity doesn't help matters. In two years we will commemorate the Somme.
The media, assisted by many of us, believe that it's our duty to resurrect these events repeatedly in the mind of the public, lest they be forgotten. But in perpetuating this merry-go-round, we can hardly blame anyone under the age of 40 for being confused.