Four in the Morning Mystery Cache

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I recently viewed an intriguing presentation on the cultural significance of this particular hour of the day. More than any other, the four o'clock hour provides the element of suspense across diverse genres of film, music, and literature. It got me thinking, along the lines of that ubiquitous PSA of yesteryear, "It's 4 AM. Do you know where your caches are?"

Use the referenced web page to answer the following questions:

1. According to poet Wisława Szymborska, the four o'clock hour is for those past what age?
2. How many letters are in title of the film trilogy George Costanza watched? Subtract one.
3. What is the last digit in the birthdate of The Simpsons creator who skipped the presentation?
4. Which letter of the ASL alphabet corresponds to the college student's "gang sign" representing four in the morning (ordinal number)?
5. How many references to four in the morning are in the works of William Shakespeare?
6. What is the year in which Simone de Beauvoir was born?
7. What month did Rives launch the Museum of Four in the Morning?
8. In which decade (19NNs) was Rives an undergraduate? Subtract two.
9. How many songs in total were on the tape?
10. According to Rives' girlfriend, what page of the book contained the poem she referenced on the tape?

Good luck!

[2016-06-08: Hint added.]

You can check your answers for this puzzle on GeoChecker.com.