Nobody sent me the memo, but apparently today is World Children’s Day. I am still not sure what that entails ” have I fallen down on my responsibility to buy a greeting card, as I frequently forget to do on Grandparents Day, Secretary’s Day and Bring Your Daughter to Work Day?

But what would World Children’s Day be without “The Concert for World Children’s Day” (7 p.m., ABC)? Musical talent, including Celine Dion, Nick Carter, Yolanda Adams, Enrique Iglesias and Josh Groban will perform. Dion, who has returned from her maternity retirement to develop her own theater in Las Vegas, will sing “That’s the Way It Is,” and “Goodbye’s (The Saddest Word).” She will also join Groban in a duet.

At the end of the show, all of the singers will gather to warble “Aren’t They All Our Children?” For those in the know, that’s the official anthem of World Children’s Day.

• Everybody loves a wedding. At least they do in the movies. “My Big Fat Greek Wedding” just may become the most popular independent movie ever released. Tonight, ABC repeats the 1997 romantic comedy, “My Best Friend’s Wedding,” (8 p.m., ABC) for the 473rd time. But in the real world, marriage seems to be in trouble. The “Frontline” documentary “Let’s Get Married” (8 p.m., PBS) looks at some staggering changes in the American family during the last generation.

“Married” begins in Oklahoma, home of the nation’s highest divorce rate. Oklahoma Gov. Frank Keating began to focus on his state’s marriage problem after experts told him that Oklahoma’s social attitudes were leading to poverty.

“Married” examines government programs to encourage stable marriages and families, instigated by Gov. Keating and the Bush administration. While many agree that solid families are good for children, some worry about government intrusion into this most private realm. Although “Married” looks at many sides of the issue, it presents the problem as uniquely American, and fails to examine high divorce and illegitimacy rates in other developed countries.

• Fans of the actress Jennifer Jason Leigh are in luck. If you like her intense, brooding performances, don’t miss the controversial 1996 child-abuse drama “Bastard Out of Carolina” (8 p.m., Lifetime), co-starring Jena Malone and Ron Eldard. On the lighter side, Leigh affects a Katherine Hepburn-like accent in the over-the-top 1994 corporate satire “The Hudsucker Proxy” (8 p.m., TNN), directed by the Coen brothers, Joel and Ethan.

Tonight’s other highlights

• A crime spree coincides with a major boxing match on “CSI” (8 p.m., CBS).
• Grace meets Leo’s folks on “Will & Grace” (8 p.m., NBC).
• A foster teen vanishes on “Without a Trace” (9 p.m., CBS).
• Abby frets about her missing brother on “ER” (9 p.m., NBC).

Series notes

• Ross discovers that the baby responds to an unusual lullaby on “Friends” (7 p.m., NBC) … An hour of amateur acts on “30 Seconds to Fame” (7 p.m., Fox) … Sissy spies on French’s secret rendezvous on “Family Affair” (7 p.m., WB).
• Dr. Cox juggles girlfriends on “Scrubs” (7:30 p.m.) … Joel revisits a pivotal block party fiasco on “Do Over” (7:30 p.m., WB)
• Dylan confesses to a crush on “Good Morning, Miami” (8:30 p.m., NBC) … On back-to-back helpings of “Jamie Kennedy Experiment” (WB), David Schwimmer appears (8 p.m.); a sham marriage proposal (8:30 p.m.).

Late night

• Pearl Jam performs on “Late Show with David Letterman” (10:35 p.m., CBS) … Jay Leno plays host to Tiger Woods and Emma Watson on “The Tonight Show” (10:35 p.m., NBC) … Tom Arnold and Mark Knopfler appear on “Late Night with Conan O’Brien” (11:35 a.m., NBC) … Martin Mull appears on “The Late, Late Show with Craig Kilborn” (11:37 a.m., CBS).