24: Legacy start Coral Peña tweeted a photo of Legacy’s finale script cover page which reveals that the final episode takes place during the hours of 11:00 P.M. to 12:00 P.M.
This means that the 24: Legacy finale will span thirteen hours in total. This is similar to the time jump in 24: Live Another Day (which had a singular time jump and spanned the hours of 10:00 p.m. – 11:00 a.m.).
The episode was co-written by showrunner Manny Coto and executive producer Howard Gordon and directed by Stephen Hopkins. If for whatever reason the series is not renewed, Hopkins will have the honor of directing the very first and very last episode of the series.
— Coral Peña (@fakecoralpena) February 13, 2017
So for those wondering how the show would cram a 24 hour day until 12 episodes, you have your answer.