Hey, where’d that decade go? “Saturday Night Live in the 2000s: Time and Again” (8 p.m., NBC) glances back at a period that seems like only yesterday. Or four months ago.

Still, viewers who like to think about the shifting zeitgeist would do well to watch this attempt to think about the George W. Bush years.

The decade begins with the political “Twilight Zone” sparked by the hanging chad controversy of the 2000 election.

“SNL” was ready made to mine comedy from the strangeness, with Darrell Hammond as Al Gore and Will Ferrell as George W. Bush.

We’re reminded here that Ferrell would leave “SNL” in 2002, leaving the show without its most capable presidential impersonator. And to drive the point home, we’re shown a revolving door of would-be Ws, one less convincing than the last. Hammond calls his attempt a professional Waterloo.

Writers and comics and “SNL” creator Lorne Michaels recall the difficulty of putting on a funny show right after 9/11. The two-hour special seems to concentrate on 2000-01 and then fast-forwards to its popular take on the 2008 election. Along the way we hear about the ascendancy of female talents Tina Fey, Amy Poehler and Kristen Wiig, among others, and the show’s symbiotic relationship with emerging YouTube videos.

While the special offers a wealth of clips from musical guests, they arrive without much introduction and seem like interstitial filler. Justin Timberlake becomes the notable exception, not because of his singing, but his participation in several memorable comedy sketches.

Those who want to know what pop music had to say in the century’s first decade will have to look elsewhere. In fact, when “SNL” wanted to make a statement right after 9/11, they turned to Paul Simon, a performer who had appeared on the very first episode of the series way back in 1975.

For all of the impersonations of politicians, “SNL” was never really about politics, as both the talent and Lorne Michaels freely admit. The attempt was to mine comedy from larger or stranger-than-life characters. The interest in the show’s 2008 political comedy was merely a reflection of the nation’s intense fascination with the race. We don’t see any clips of a Bush-Kerry 2004 fake debate. As Michaels explains, “SNL” couldn’t generate much interest in the characters.

Other tea-leaf readers will have to determine whether “SNL” has become too dependent on political parody. And whether its brand of character-based humor can compete with other forms of absurd political theater, from Jon Stewart to Glenn Beck.

Tonight’s other highlights

• Robert Englund guest stars on “Bones” (7 p.m., Fox).

• An accelerated wedding schedule for Demetri and Zoey on “FlashForward” (7 p.m., ABC).

• Hodges and Wendy become mentors on “CSI” (8 p.m., CBS).

• “Secret History of the Atom Bomb” (8 p.m., National Geographic) looks at the weapon’s development and proliferation.