David Letterman deserves a prime-time celebration for all he’s done in the other TV dayparts: daytime television (briefly), and late-night TV (for a full third of a century). And here it is: a 90-minute retrospective special on CBS, the network that has been Letterman’s home for the majority of that lengthy, impressive, entertaining run. Oh, and my own salute, by the way, runs today on NPR’s Fresh Air with Terry Gross. Oh, and tonight at 11:35 ET on Late Show with David Letterman, by the way, the scheduled guest is… President Barack Obama.