"Colin Youngs" wrote in message
...
At Longyearbyen on Svalbard (Spitzbergen) the midnight sun runs from 20th
April to 24th August

http://www.timeanddate.com/worldcloc...th=4&year=2011
&obj=sun&afl=-11&day=1

It's interesting to see how rapidly the length of the night increases once
the sun does go below the horizon again.

In the extreme case, at the North Pole, night length changes from zero to
24 hours at the equinox in September (actually a few days later due to
refraction appearing to 'raise' the sun).