'Last Week Tonight' debuts in Trump's America, where it will fight for the existence of facts

Sanity, thy name is John Oliver. Last Week Tonight began its fourth season on HBO on Sunday after a hiatus that began on Nov. 13, 2016 — a simpler, if still fraught time.

"Normally, we like to focus this part of the show on complex, depressing policy issues," Oliver said after an opening segment about Trump's presidency so far and how he can't seem to shake people's hands. Instead, Oliver focused on Donald Trump's assault on the very concept of reality, and devoted the rest of his show to investigating how and why Trump lies so much — and what can be done to fix it.

"Trump was telling the truth about his solutions to the problems he was lying about, and he is now making real policy based on fake facts," Oliver said.

In the 20-minute segment that follows, Oliver fact-checks some of Trump's most outlandish statements and where he gets his information.

Because Oliver and his team consistently put their money where their mouths are, the show debuted several commercials and purchased air time on cable news in the D.C. area. The ad subjects range from the nuclear triad to the name of Tiffany Trump, whose existence her father often seems to forget.