After a hard days work, I came home, had a small drink with dinner and feeling rather tired, I went to bed at at 8:00pm and by 8:30pm I was fast asleep having previously set my faithful wind up alarm clock to awaken my at 9:30am. Given I was tired and I slept right through until the alarm awoke me, how long did I sleep?

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1 hour. Faithful wind up alarm clock's cannot tell am from pm so it woke me up a mere 1 hour later at 9:30pm.

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