The Nature of Things
Scientists explore the effect of artificial light in the new documentary Lights Out. The type of light humans are exposed to between dusk and bedtime can cause problems by cancelling out the health benefits of darkness. CBC, 8 p.m.
Enjoy the holiday hijinks of the Dunder Mifflin staff in a special Dwight Christmas episode. Dwight decides to pick up the slack and provide his own version of holiday cheer after the party-planning committee falters. NBC, 8 p.m.
In the new episode Happy Birthday, Mr. President, an unexpected catastrophe forces Olivia to return to the White House. The first few days of Fitz's presidency are also examined. ABC/Citytv, 9 p.m.
Jay Leno: Bill O'Reilly, Krysten Ritter
David Letterman: Bill Murray, Vintage Trouble
George Stroumboulopoulos: Rita MacNeil
Craig Ferguson: Denis Leary, Richie Sambora
Jimmy Fallon: Tom Selleck, Richard Branson
The Daily Show: Gov. Chris Christie
Jimmy Kimmel: Chris Rock, Kelly Ripa (right)
Conan O'Brien: Ty Burrell, W. Kamau Bell