Salt

Evelyn Salt (Angelina Jolie) is being tortured in a North Korean prison on suspicion of being an American spy. Her boyfriend, arachnologist Mike Krause (August Diehl), generates so much publicity that the CIA is forced to arrange a prisoner exchange, despite the agency's policy against it. Salt's CIA colleague Ted Winter (Liev Schreiber) greets Salt at the border. As they drive away, Mike proposes marriage, despite Salt's admission that she is in fact a CIA operative.
Two years later, on Salt and Mike's wedding anniversary, a Russian defector named Oleg Vasilyevich Orlov (Daniel Olbrychski) walks in to Salt's office. Salt interrogates him, with Winter and CIA counterintelligence officer Darryl Peabody (Chiwetel Ejiofor) observing. Orlov claims that, on "Day X", highly trained Russian sleeper agents known as "KAs" will destroy the U.S. Orlov tells them that Agent "KA-12" will assassinate Russian president Boris Matveyev (Olek Krupa) at the funeral of the American Vice President. Orlov reveals that KA-12 is named Evelyn Salt, and lie detectors confirm his entire story. Peabody orders Salt be detained, but Orlov kills two agents and escapes. In the confusion, Salt is able to escape as well, running barefoot through the street. While she is being chased, she discovers that Mike was kidnapped.
Later, at the funeral, Salt appears to succeed in killing President Matveyev, and then surrenders herself. Matveyev is declared dead. Salt escapes again and heads to a barge where Orlov is hiding with other sleeper agents. In a series of flashbacks, Salt recalls growing up in the Soviet Union and being trained with other children. On the barge, Orlov welcomes her back and has Mike killed in front of her. When Salt shows no reaction, Orlov is convinced she is loyal and begins briefing her on her next mission. She is to rendezvous with another KA who will help her assassinate the American president. Salt then kills Orlov and all of the other agents on the barge. She then meets with KA Shnaider (Corey Stoll), who uses his cover as a NATO liaison to get Salt into the White House. Once inside, Shnaider launches a suicide attack to force agents to move the President (Hunt Block) to an underground bunker, accompanied by Winter. Salt follows them and manages to enter the bunker before it is sealed.
The US President learns that Russia has mobilized its nuclear arsenal in response to their president's death. He orders American nuclear weapons readied in response. CIA Agent Winter then suddenly kills everyone except the President and introduces himself as Nikolai Tarkovsky, another KA. Winter incapacitates the President and begins aiming nuclear missiles at Mecca and Tehran to incite millions of Muslims against the United States. Salt tries to persuade Winter to let her inside the sealed room, but then he sees a television report that President Matveyev is alive and well: Salt had used spider venom to cause a simulated death of Matveyev. Winter refuses her entry and reveals that Mike's kidnapping and her blown cover were his idea. Winter plans to place full blame for the nuclear attacks on Salt. Salt breaks into the room before he can launch the missiles. The two wrestle for control of the nuclear football, with Salt aborting the missile strikes before being captured.
As Salt is being led out in chains, Winter grabs a pair of scissors, apparently to attack her or to defend himself if necessary. She unexpectedly hooks her chain around Winter's neck and jumps over the stair railing, choking him to death. On the helicopter ride to be interrogated, Peabody questions her. Salt explains that she killed Winter because he orchestrated the death of her husband, and promises to hunt down the remaining KA agents if freed. Peabody is convinced after receiving a text that Salt's fingerprints were found on the barge where the sleeper agents were killed, supporting her story. Salt is allowed to escape, jumping out of the helicopter into the river below and escaping into the woods. In an alternate ending Salt jumps out of the helicopter and arrives in disguise at the place where she was trained as a child in the Soviet Union, she is then seen by the water as the place blows up and Salt smiles.

Question: When are Russian sleeper agents supposed to destroy the U.S.?
Answer: Day X