Unlike with other Yahoo Answers crossovers, I don’t think Ray Eston Smith Jr is a current contributor here on Shakespeare Geek. But this seemingly simple question, and his lengthy detailed answer, fascinate me.
Mr. Smith (Eston Smith?) states as fact that Hamlet was 30, and then enumerates all the clear instances within the play where Shakespeare tells us. Including:
* The "30" is also mentioned in "The Mousetrap," where the Player-King said to his queen, "thirty dozen moons with borrow'd sheen about the world have times twelve thirties been" since their marriage. This is meant to signal 30 years, thus relating the Player-King to Hamlet's father.
* King James VI of Scotland, in his private correspondence, liked to use code-numbers in case his letters were intercepted. His code for himself was "30." There are many parallels between Hamlet and James VI.
* Hamlet wanted to go "back to school in Wittenberg." That doesn't mean he was a student. At age 30, he may have been a tenured professor. (Did they have tenure in those days? It doesn't matter, they didn't even have a university in Wittenberg in Hamlet's days. …Hamlet just wanted to go back to Wittenberg where, at age 30, he was well-settled.
I’d never heard some of those before, particularly the James VI thing. There is debate in the comments, although people seem to agree that the gravedigger scene clearly says he’s 30.