24 is Agile

The director speaking in a short film from the bonus DVD of Season 2 of 24:

In that 12 hours I gotta figure out how I'm gonna achieve everything I need to achieve in blocks of two hours and three hours. We do what's called a timeline, and we give ourselves a certain amount of hours to work on every scene. And we need to try to get to those hours to make our day--to stay within our 12 hours of shooting time.

Then as the day goes on you're constantly changing--things aren't working out, you look for a shorter way. A sort of more economic way to shoot a scene.

Keifer Sutherland speaking in the same short film:

When you actually put something on its feet, logic issues will come with the physicality of the scene that might not come up when you're simply reading it. Stuff hopefully is continually changing until the very last moment until we shoot it, and I think your ability to adapt in those specific situations and certainly adapt at speed in many cases is the difference between your ability to do something well and not.