Economist editor Daniel Franklin details the most pressing issues the world faces in 2013. Then Rupert Holmes, who wrote the book, music, and lyrics for “The Mystery of Edwin Drood,” will be here along with two of the play’s stars: Jim Norton and Jessie Mueller. Jay Neugeboren talks about his latest novel, The Other Side of the World. And, mark the date! Because today’s Please Explain is all about calendars.