On June 21, as seen from the North pole ...
-- the sun has been up, and it's been light outside, 
for the past three months ... ever since March 21 . 
-- The sun won't set, and it won't be dark outside, 
for another three months ... until September 21.
-- Here at the North pole, it stays daylight for six months straight.
Today, on June 21, we're exactly halfway through the period of 
continuous daylight.