The only episode in the 24 series to state the episode takes place less than one hour.
When Mark Bourdeau is looking at the computer files on Jack, he reads through a list of names of Jack's confirmed kills throughout his career at CTU. The first name on the list is Ted Cofell. Cofell was the Serbian finance manager that Jack encountered during Day 1 of the original series. Though his name is first on this list, Jack didn't actually kill him. Cofell suffered from a heart condition that was exacerbated by Jack's interrogation. His death was satiated by his own refusal to take his medication, which Jack offered to him.
The door code Chloe enters to gain access to Open Cell's headquarters is "2-4-9," appropriate for what was essentially 24's 9th season.