Dragon Hour is the time just before darkness, when the fading/failing light makes it near impossible to focus your eyes. It is easier to see where you are going in actual darkness because your eyes can adjust to this.
'Dragon' comes from the film 'Reign of Fire' in which the character, 'Denton Van Zan' explains this hour...

"You see they (the dragons) have great vision during the day, and even better vision at night. But in the failing light, they can't focus. Magic hour."
Luke: "I can't see where the fuck i'm going!"

Joe: "It's Dragon Hour man, no-one fucking can!"
by J R Hurn September 22, 2007
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