The Ad Club of New York confirms the accuracy of the show's account of the awards ceremony being held the night of Martin Luther King assassination, April 4th, 1968, and how it was interrupted with the news of King's death. This includes Paul Newman speech about his support of presidential candidate, Eugene McCarthy.
The real estate agent tells Peggy that getting to her prospective apartment on the Upper East Side will be easier, and that its value will quadruple once the Second Avenue subway is completed. Non-New Yorkers may not realize that this reference is meant to be a joke. This subway line was originally proposed in 1929, and efforts to fund it and build it have come and gone over the years with little result. At the time this scene in Mad Men was set (1968), funding had been secured, but New York City's fiscal crisis in the 1970s caused construction to be halted for lack of funds. Construction didn't resume until 2007, with the unfruitful hope that it would be completed by 2012. In January 2017, the first stations along this line opened as an extension of the Q line; at that point there were only three stops on the Second Avenue Subway line: at 72nd, 86th, and 96th Streets.
Ginsburg uses the term "alter kockers" when he and his date are commiserating about how they were set up on their blind date. The term is Yiddish, and loosely translates to "old sh*tters" -- the American English equivalent is "old farts."
This episode refers to several instances of rioting and self destructive behaviors and Don takes Bobby to see Planet of the Apes (1968) in which human civilization has been destroyed.
This episode takes place in April 1968.