In HBO’s season-two trailer for Silicon Valley, a hulking, Birkenstock-wearing computer programmer grabs an enormous bong and fires it up to the relentless strains of Danny Brown’s “Smokin’ & Drinkin.’”

The series, which returned April 12, is but one of many premium, basic-cable and broadcast shows in which weed plays into the story line in one form or another. In Comedy Central’s Broad City and Workaholics; Showtime’s Episodes; IFC’s Maron; and even A&E’s Bates Motel, where the local town is run by a weed cartel, getting high is just something people do. On a fairly regular basis. And the act is not just implied or covered by a jump-cut to the after-effects; characters are casually toking away on screen.

Download the 4/20 timeline.

With 23 states and Washington, D.C., having legalized marijuana in one form or another, TV programming has gone to pot as well. Since the earliest references to weed in scripted TV shows to today, pot-related story lines have evolved from “Protagonist smokes weed — with disastrous results” to “with nostalgic results” to “with comic results” to, essentially, just “Protagonist smokes pot.” It’s tangential to the results.

Is TV merely reflecting the nation’s changing attitudes about pot or are we a nation under TV’s influence? In an effort to answer this 4:20-inspired question — that being the legendary time of day stoners would gather after school to get high, making the date April 20 a totem on the stoner calendar — Multichannel News presents this “4/20 Timeline” looking at the concurrent evolution of pot and plot.