When did Friday become news night? All three major networks now regularly schedule newsmagazines on Friday nights. PBS has a history of airing business and political talk shows on Fridays, and now they have Bill Moyers and Tucker Carlson as ideological bookends.

Tonight, “20/20” gives way to the “Peter Jennings: Guantanamo” (9 p.m., ABC) special report that investigates the fates of more than 600 prisoners from 40 countries who have been held without legal rights or representation for years. Is this a necessity of the war on terror or a threat to the Constitution? As this program was being prepared, the Supreme Court was deciding on two landmark cases challenging the detentions.

This is a very serious matter. But can network news still cover serious issues? Does this Jennings report lose any credibility because it airs in the same “20/20” time slot where, just last week, we were treated to Madonna’s thoughts on mysticism and her decision to take the new name “Esther”? Did NBC’s “Dateline” lose all credibility after its orgy of fluff for “Friends” and “Frasier” finales? And can CBS really call Julie Chen a news correspondent when she’s best known as host of “Big Brother”?

Network television news is not just suffering from self-inflicted wounds. Fox News continues to claim that that they offer the only alternative to the mainstream media “liberal bias.” Just how anyone could watch television news present a weeklong canonization of Ronald Reagan and still detect such a slant is beyond me. Perhaps the time has come for fair-minded folks to inter the myth of liberal bias.

Tonight’s other highlights

• Household chores come divinely inspired on a repeat of “Joan of Arcadia” (7 p.m., CBS).
• Rob Lowe, Andre Braugher and Donald Sutherland star in the 2004 remake of Stephen King’s vampire novel “Salem’s Lot” (7 p.m., TNT).
• A man stands trial for killing his mail-order bride on a repeat of “The Jury” (8 p.m., Fox).
• Scheduled on “48 Hours Investigates” (9 p.m., CBS): a teen travels halfway around the world to meet a stranger from a chat-room encounter.
• An action-film shoot turns deadly on a repeat of “Las Vegas” (9 p.m., NBC).

Late night

Bonnie Hunt and Dylan Moran appear on “Late Show with David Letterman” (10:35 p.m., CBS) … Jay Leno greets Keenan Ivory Wayans and Marc Anthony on “The Tonight Show” (10:35 p.m., NBC).