Day 2: 6:00 A.M.-7:00 A.M. - S2-E23
Continuity mistake: When Kate Warner ascends the stairs in Kim Bauer bosses house, she holds her sunglasses in her left hand. When the camera changes she has sunglasses on her right hand and her left hand is empty.
Day 2: 7:00 A.M.-8:00 A.M. - S2-E24
Continuity mistake: During the showdown between Jack and Kingsley at the colloseum, the shadows made by the early morning sun change throughout the sequence. By the time the SWAT-team arrives, the sunlight comes from the other side entirely. (00:20:50 - 00:29:45)
Day 2: 7:00 A.M.-8:00 A.M. - S2-E24
Continuity mistake: At the end of E23 Jack and Mrs Palmer crash their SUV. It shows the right front hubcap fly off. At the beginning of E24, when Jack tries to start the car, it is back on.
Day 3: 6:00 P.M.-7:00 P.M. - S3-E6
Continuity mistake: When Chase calls Chappelle from his car, his mobile shows the date and time "Sep 4. 03 (Thu) 2.15pm" rather than the actual time 06:09, which is displayed seconds later on screen. (00:09:10)
Day 3: 1:00 A.M.-2:00 A.M. - S3-E13
Continuity mistake: In the scene where Alan Milliken has collapsed, his right arm is bent across his chin, while in the next shot, when Julia steps over him, his arm is above his head. (00:37:00)
Day 3: 1:00 A.M.-2:00 A.M. - S3-E13
Continuity mistake: When Jack leaves the cockpit he puts his gun away in a holster on his back. When he gets back to Nina and Chase he puts his gun away a second time.
Day 3: 2:00 A.M.-3:00 A.M. - S3-E14
Continuity mistake: Chappelle shows Jack the security footage of him shooting Nina. He shoots her three times. He fires the gun with more of a gap between the gunshots on the footage than he did when we saw him kill her.
Day 3: 4:00 A.M.-5:00 A.M. - S3-E16
Continuity mistake: When Michelle shoots the escaping hotel customer, her gun shows a jammed shell casing while she points her gun at him. The jammed casing wasn't there after she fired her final warning shots and disapears suddenly just before she shoots him down. (00:39:00)
Day 3: 7:00 A.M.-8:00 A.M. - S3-E19
Continuity mistake: When Kim is working undercover, dressed up in Saunder's daughter's clothes, she comes out of the Ladies' toilets wearing brown trainers. As she sits down at the library computer, you see she is wearing her very high heeled shoes. A few seconds later, as she is walking between the library shelves, she is wearing brown trainers.
Day 3: 8:00 A.M.-9:00 A.M. - S3-E20
Continuity mistake: When Jane Saunders gets into the car to go to CTU she and Kim have switched clothes again. Though the top worn by Jane is not the same as the one she wore earlier, which Kim then used. It's similar but not identical.
Day 3: 9:00 A.M.-10:00 A.M. - S3-E21
Continuity mistake: When Tony locks down Tech One from his office, the CCTV screen he's watching shows the monitors in there displaying the "locked down" message moments before they actually change to the message in the next shot within Tech One. (00:36:40)
Day 3: 10:00 A.M.-11:00 A.M. - S3-E22
Continuity mistake: During the hostage exchange, there is a shot of the black man waiting for Jane Saunders to walk to him, in the background we can just see a man stood behind a car door. However, in the wider shots and when Saunders jumps out of his car, the man is not there.
Day 3: 11:00 A.M.-12:00 P.M. - S3-E23
Continuity mistake: In the scene where Wayne and Fox are in Sherry's house searching for the pill container, right before Sherry asks, "What's going on here?" Wayne is seen wearing latex gloves. The camera then cuts to Sherry. When it cuts back to Wayne, his gloves have magically disappeared.
Day 3: 12:00 P.M.-1:00 P.M. - S3-E24
Continuity mistake: In the teachers' lounge Jack tells Chase that the second floor is cleared. When he doesn't get an answer he realises something is wrong and runs down to the floor Chase is searching. After he's cut Chase's hand off he runs out into the hallway and into the lounge which is suddenly on the same floor Chase was on.
Day 4: 8:00 A.M.-9:00 A.M. - S4-E2
Continuity mistake: When Agent Lobell tries to stop a car from leaving the train station, the terrorist in the car shoots at him through a window, shattering it. When the camera cuts to a shot of Lobell falling to the ground, the window in the car is gone, but no fragments of it are on the car or the ground under it.
Day 4: 11:00 A.M.-12:00 P.M. - S4-E5
Continuity mistake: Debbie's gunshot wound travels up from her navel to right under her thorax within 40 seconds. (00:15:00 - 00:15:40)
Day 4: 11:00 A.M.-12:00 P.M. - S4-E5
Continuity mistake: When the cop in the car reaches to his microphone, his right hand is empty. When he types into the keyboard one second later, he is suddenly holding a pen between his fingers. (00:22:05)
Day 4: 12:00 P.M.-1:00 P.M. - S4-E6
Continuity mistake: Day Four: 12:00 PM - 1:00 PM. When Tariq and Behrooz are shown in split-screen digging Debbie's grave right after the commercial break (12:54:10 by the show's clock), Tariq's white t-shirt is covered in dirt. When the shot goes back to them a minute or so later, Tariq's t-shirt is much cleaner.
Day 4: 1:00 P.M.-2:00 P.M. - S4-E7
Continuity mistake: When we first see the map of the powerplants that are successfully shut down (green) all the plants in Minnesota are green. Towards the end, however, one of them is shown flashing red, meaning it has not been shut down.
Day 4: 2:00 P.M.-3:00 P.M. - S4-E8
Continuity mistake: When James phones Jack, who is at Tony's house with Audrey, Jack says they are at "21408, Kipling, North Hollywood". Later, when Secret Service arrives to pick up Audrey, Jack walks outside the house, where we see the house number is actually 21048. The same can be seen earlier when Tony, Audrey and Jack first arrive at the house, but not as close-up. (00:25:05 - 00:30:05)
Chosen answer: Nobody knew, not even the writers, until at least halfway through the season when they were writing the end. They wanted to keep all options open.
Nick N.