Hillary Clinton has told voters the presidential election is a "moment of reckoning", as she made history by accepting the Democratic nomination.Speaking on the final night of the party's convention in Philadelphia, the first woman nominated by a major party said there were huge challenges. "Powerful forces are threatening to pull us apart," she said.Mrs Clinton accused her Republican opponent in November's election, Donald Trump, of sowing discord."He wants to divide us - from the rest of the world, and from each other."