Mad Men is back, which is great. In addition to the multilayered work of Matthew Weiner and his cohorts on the series, the accompanying history and popular culture are concomitant joys of that show; it’s fun to work out when a particular episode is set and run down the attendant details. Season 6’s opener, “The Doorway,” happens at the end of December, 1967. “Hey,” some folks said, “What about the Summer Of Love”? Having Season 5 end before it started and Season 6 starting after it was over was a deliberate choice Matthew Weiner made, and it’s not tough to see why. The Summer Of Love happened in San Francisco — miles away, both geographically and psychically, from Manhattan, Rye NY and Madison Avenue specifically. Weiner said his specific reasoning for that choice was that the come-down and “hangover” offered a richer range of dramatic possibilities than the groovalicious summer months of 1967.