It's a sign of the times: Don Draper meets a drunk Army private, about to get married, in Hawaii. They bond over shared service. Or at least the private thinks he's bonding with the ever elusive Don. He talks about what his machine gun can do to a water buffalo. Don asks how long he'll be in Vietnam. Eight months, the private declares. The war, which had lurked in the background of Mad Men seasons past, is now front and center. The danger is there. The danger is real. And soon enough Peggy Olson will be confronting Vietnam... in an advertisement for earphones. It is Christmastime 1967, and 1968 is just around the corner. If you thought contemplating death was morbid, the worst is yet to come.

Sunday night's season-six Mad Men premiere—which we can, at last, talk about in full—was, from the outset and through the end, very much of a different era than the Mad Men that first captured America's attention. The buttoned-up perfection of the clothing is gone. The color palette seems brighter, groovier. Megan has a fondue pot. Roger's going all Woody Allen. Ginsberg has a mustache. Harry and Pete have sideburns. (Pretty much everyone has sideburns.) And pot is everywhere: Megan wants to have sex with Don while they're high, Betty asks Sally's friend if she's on "dope," Joan smells "reefer," the creative team is smoking in the office. The Summer of Love, 1967, has come and gone, never to be recorded in the official Mad Men record as the show's historical context—at once subtle and yet always looming—heads deep into the shadows of a complex year.

By December 1967 Vietnam had escalated to the extent that there were already almost half a million U.S. troops in South Vietnam. The North Vietnamese would launch the Tet Offensive in late January 1968, and on February 1, Chief Brigadeer General Nguyen Ngoc Loan executed a Vietcong guerrilla in a photo that would arguably become the most famous of the war. By March, the My Lai massacre has happened. American opposition to the war was growing, which we can tell, from hints in the two-hour Mad Men premiere, got more and more vocal. Peggy, most directly obviously, has to contend with this, when a comic jokes on The Tonight Show about GI-named necklaces made from Vietcong ears—very much a real thing. (And not just the necklaces: Via New York's Matt Zoller Seitz, we learned that one blogger has identified the comic as Milt Kamen, who appeared on an episode guest hosted Phyllis Diller on December 22, 1967.)

But aside from the anti-war sentiment, elements of subculture made their voices known on Mad Men Sunday night. Don hates an ad for Dow oven cleaner. The company wants it to include the word "love." Presented with an illustration of newlyweds, he fumes: "This couple doesn't exist." The new lady copywriter asks: "What are you asking for? A little Haight-Ashbury colonial?" In 1968, Tom Wolfe published The Electric Kool-Aid Acid Test, the definitive text on Ken Kesey and his Merry Pranksters. Betty Francis, meanwhile, comes into contact with East Village squatters on St. Marks Place when looking for Sally's disappeared friend, Sandy. In 1967, the Electric Circus, a club where the likes of the Grateful Dead played, opened at 19-25 St. Marks Place, with The Village Voice calling it "the latest total environment, McLuhanist discotheque." Here are some photos of the club in 1968. Photographer James Jowers captured this image of the famous local in 1968: 

Of course, 1968 matters, and Mad Men will have much to draw from, even if it again doesn't make it past spring. The assassination of Martin Luther King Jr. arrives in early April. The assassination of Robert F. Kennedy comes two months later. In New York, Columbia students shut down the University. There are riots at the Democratic National Convention. Richard Nixon wins the presidency. And, of course, the way Mad Men approaches major cultural events is often subtle. It's a show that cares as much—or more—about its characters as the distinctive time period in which they live, so events tend to take a backseat to their story lines. It's no use guessing how Don and Megan might hear about RFK's death (assuming they are still even together), at least if you use as a template the season three episode "The Grown Ups," which dealt with JFK killing: Roger's daughter got married, Betty sees Lee Harvey Oswald get shot on television, and then she pushes Don away. 

And still it's difficult not to wonder what, exactly, 1968 will mean to Mad Men. This is the end of the era in which men like Don Draper thrived. Now that the season is underway we have even more questions: Will someone start to protest? How will the show continue to confront the civil-rights movement? Will someone get drafted? Will the firm start to work for Nixon again? They did in the first season, after all...