Fifteen years ago, on Nov. 6, 2001, “24” premiered on Fox. It was less than two months after the terrorist attacks of Sept. 11, and the country was still grieving, perhaps craving a series where the U.S. was, at the end of the day, victorious against the forces of terrorism.

The format was unlike anything that had been done before: Each of the 24 episodes of the season would occur in “real time,” totaling up to a very, very long day for protagonist Jack Bauer (Kiefer Sutherland).

But “24” co-creator Joel Surnow wasn’t sure the audience would bite. “Real time was an unproven concept,” Surnow wrote to Variety. “We had no idea if it would have the desired effect — which was to create a heightened sense of urgency. We couldn’t even gauge it when the picture was cut together. It wasn’t until the final mixing session — with all the music and effects in — that we saw what this show could be. It worked.”

Over the next nine “days,” it won 18 Emmys — including a best actor trophy for Sutherland — and became a cultural touchstone. The series also ignited a conversation about the portrayal of terrorists and torture on television.

In honor of the 15th anniversary of the “24” premiere, Variety asked the executive producers to choose their favorite hour from each of the eight seasons and limited series “24: Live Another Day.” The continuation of the series, “24: Legacy,” will premiere after the Super Bowl on Fox on Feb. 5, 2017.

Day One

Evan Katz: “11 p.m. – 12 a.m.” Ruthless twists, and a bold ending with Teri Bauer dying.

Howard Gordon: “12 a.m. – 1 a.m.” My favorite episode of the first season is the pilot. Not only did [co-creators] Joel [Surnow] and Bob [Cochran] prove their concept of real-time storytelling here, they also created a vivid cast of characters, especially Jack Bauer, who would become one of the most iconic heroes on television.

Manny Coto: “11 p.m. – 12 a.m.” Jack’s wife dies! A shocking, devastating finale that enshrines “24” as a show that goes where others fear to tread.

Robert Cochran: “12 a.m. – 1 a.m.” I have to go with the pilot episode, which launched the series, established the real-time format, and introduced Jack Bauer.

Day Two

Evan Katz: “10 p.m. – 11 p.m.” George Mason finally does the right thing, after many hours of weaselly behavior. And the bomb.

Howard Gordon: “8 a.m. – 9 a.m.” Having done it a few times myself, I’ve come to recognize the unique challenges the first episode of each season of “24” presents. These episodes have to explain where our characters have been emotionally and what they’ve done in the intervening months or years, and set up a compelling and exciting story that will carry us for the next 24 hours. So for me, the opening episode — “8 a.m. – 9 a.m.” — really delivered.

Manny Coto: “10 p.m. – 11 p.m.” The cowardly and corrupt George Mason flies a nuclear bomb into the desert, saving hundreds of thousands of lives. One of the best moments in the series.

Robert Cochran: “10 p.m. – 11 p.m.” Jack bids farewell to Kim, while undertaking a suicide mission to detonate a nuclear bomb in the desert outside Los Angeles — something most viewers probably didn’t think we would really do.

Day Three

Evan Katz: “6 a.m. – 7 a.m.” Jack executes CTU Director Ryan Chapelle. You actually feel worse for Jack than Chappelle.

Howard Gordon: “6 a.m. – 7 a.m.” For me, that conundrum was quintessential “24,” and pushed the limit of just how far Jack would go. That Chapelle wasn’t especially heroic — in fact, he was the opposite — really underscored the pathos and tragedy of the episode. Also, the episode took place during one of the signature hours of the show, transitioning from night to day — which was ironic, considering that Jack’s character became irrevocably darker.

Manny Coto: “6 a.m. – 7 a.m.” Because I’m convinced that Jack never really shot Chappelle in cold blood, and that he’s going to show up alive in “24: Legacy.”

Robert Cochran: “6 a.m. – 7 a.m.” At the direct request of President Palmer, Jack has to perform one of the most gut-wrenching acts of his life — killing an innocent colleague in order to buy time to find the terrorist who controls a plague virus. Kiefer’s acting brilliantly portrayed the costs such acts were exacting on the character’s soul.

Day Four

Evan Katz: “2 a.m. – 3 a.m.” Jack’s actions directly result in the death of his girlfriend Audrey’s ex-husband. And you feel worse for Jack than for Audrey or her ex.

Howard Gordon: “12 p.m. – 1 p.m.” This season unfolded in an especially complicated and, at times, absurd way. This episode was emblematic of this roller-coaster storytelling, pivoting from the Audrey/Heller kidnapping to the broader threat presented by the Dobson Override and the nuclear energy infrastructure.

Manny Coto: “11 p.m. – 12 a.m.” Air Force One is shot down by a stolen Stealth fighter, paving the way for President Logan, one of the greatest characters in the series.

Robert Cochran: “11 p.m. – 12 a.m.” A somewhat unusual episode, featuring the point of view of two non-recurring characters — an innocent couple on a camping trip, who are astounded to find themselves in possession of the nuclear “football” after Air Force One makes a crash landing in the desert.

Day Five

Evan Katz: “6 p.m. – 7 p.m.” Edgar Stiles, a beloved CTU employee, dies a sad, silent death. And you feel the loss more than you expect.

Howard Gordon: “7 a.m. – 8 a.m.” For some of the same reasons I mentioned above about the first hour of every season, this one stands out as my favorite episode. We recognized the risk of ending David Palmer’s life in the first five minutes of the episode, and it was hard to say goodbye to Dennis [Haysbert] and to Palmer, who is among my favorite characters. But the reverberations of that loss played through and paid off in a way I’m really proud of, and allowed us to tell the story of Charles Logan, played by the brilliant Greg Itzin.

Manny Coto: “3 a.m. – 4 a.m.” A passenger jet lands on the 118 freeway, passing very close to the “24” production offices.

Robert Cochran: “7 a.m. – 8 a.m.” The deaths of David Palmer and Michelle Dressler were sudden and shocking but dramatically coherent, and essential to the storyline of what many regard as the show’s best season.

Day Six

Evan Katz: “5 a.m. – 6 a.m.” Jack says goodbye to Audrey, we think for the last time. A soulful last moment of the season for Jack.

Howard Gordon: This season was maligned by critics and fans, but there was a real challenge with where we’d left Jack. He had pretty much lost everything he had to lose, so in many ways he was like a walking ghost and even welcomed the chance to sacrifice his life. There’s no episode that stands out to me.

Manny Coto: “9 a.m. – 10 a.m.” Rush hour isn’t even over and Valencia’s already been blown up by a suitcase nuke.

Robert Cochran: “5 a.m. – 6 a.m.” Jack’s “’Casablanca’ moment,” in which he realizes the best thing he can do for the woman he loves (Audrey Raines) is to disappear from her life.

Day Seven

Evan Katz: “7 p.m. – 8 p.m.” Tony Todd and fellow Sanglan commandos storm the White House. A favorite because, I repeat, Tony Todd storms the White House.

Howard Gordon: “8 a.m. – 9 a.m.” Coming off Season 6, we really felt the pressure. It was a do-or-die proposition, and we had a terrible time in the writers room coming up with a story that worked. We took a bunch of false starts that delayed production, and I was as close to a nervous breakdown as I’ve ever been. So again, I’d have to go with the season opener as my favorite of a season that got the show back on track.

Manny Coto: “7 p.m. – 8 p.m.” “24” reveals that it’s possible to invade the White House by scuba-diving underneath it.

Robert Cochran: “8 a.m. – 9 a.m.” Jack, unflinching and unapologetic, faces down a Congressional inquiry, and we learn that Tony Almeida, presumed dead since Season 5, is not only alive, but working for the forces of evil.

Day Eight

Evan Katz: “3 p.m. – 4 p.m.” The finale. Chloe turns off the eyes in the sky to let Jack escape. A fitting end, which turns out not to be…

Howard Gordon: “3 p.m. – 4 p.m.” Launching a successful series is tough, but knowing when and how to end it has its own unique challenges. It definitely haunts the minds of a lot of showrunners. I was really pleased with the series finale (at least we thought would be the series finale at the time), and with the final image of Jack on Chloe’s big screen, a fugitive forced to flee the country he saved eight times.

Manny Coto: “3 p.m. – 4 p.m.” In the final moments of the series (or so we thought), Chloe bids farewell to Jack, and America is a little less safe.

Robert Cochran: “3 p.m. – 4 p.m.” Chloe talks Jack out of taking revenge on a foreign leader, thus avoiding an international crisis. Then, concluding a character arc which began with the show’s very first episode, Jack, disillusioned and feeling that his actions over the years, justified or not, have made him an outcast, vanishes forever (well, OK, not quite forever).

“24: Live Another Day”

Evan Katz: “6 p.m. – 7 p.m.” President Heller appears to sacrifice himself in Wembley Stadium in order to save London. Dynamite performance from William Devane.

Manny Coto: “7 p.m. – 8 p.m.” Jack throws Margot out the window without even informing her of her Miranda rights.

Robert Cochran: “11 a.m. – 12 p.m.” Jack, a fugitive for the last four years, is “captured,” but his capture is not what it seems. Many characters from previous seasons reappeared in completely new configurations, providing a fresh start to the reboot of the series.