What exactly is the "Bronze Age" of comcs?

I've got a friend with a theory that defies mathematics.
Even though the 1970s came to an official end on Dec. 31, 1979, it took a few more years before the decade really gave up the ghost. He argued that the 1970s didn't end until sometime in 1982. Taking the flawed math into account, I suggested a better date: May 25, 1983 ... the day Return of the Jedi was released.
Comic book "ages" are even more difficult to pin down, because we don't have music, movies, politics and fashion as guideposts. In comic books the tides change at a glacial rate, and many times fans have found themselves in a world, much like Howard the Duck, that "they never made."
Over at Wikipedia, editors have picked very loose dates for the Bronze Age, pinning it loosely to "the early 1970s to the mid 1980s." It was a period neither marked by the unprecedented imagination of the 1960s, nor the cynicism of the so-called "Dark Age," ushered in by books like Watchmen, The Dark Knight Returns and The Punisher: Circle of Blood (though these books are less to blame than the artists and writers who made careers out of misunderstanding these books.)
If the Bronze Age has any one defining aspect, it was an attempt to bring counterculture attitudes into the mainstream. Books like Omega the Unknown, Howard the Duck, Tomb of Dracula, Silver Surfer, The New Gods and Conan the Barbarian brought a rebellious literary quality to a medium often cited as a beacon of illiteracy. Until the early 1970s, the mythic qualities of comic books had mostly been a product of the subconscious. During the Bronze Age, though, many writers and artists actively explored these subtexts and merged fantasy and reality in a way never seen before in the medium. What had begun as unassuming morality plays for children quickly evolved into murky, often violent philosophical explorations. Which is why, for many people, the Silver Age of comics came to an end in 1973, when Gwen Stacy died in Amazing Spider-Man 121.