In "A Good Day to Die Hard," Jack McClane had been undercover in Russia for three years.
Jack is initially presented as a troubled son who has been arrested after an apparent assassination attempt in Moscow. John McClane travels to Russia expecting to help him, only to discover that Jack is actually a CIA operative working under deep cover.
Jack's mission involves getting close to Yuri Komarov, a political prisoner whose hidden file could expose corrupt Russian official Viktor Chagarin. Jack deliberately creates a criminal identity and even arranges to testify against Komarov so he can remain near him.
A common mix-up is confusing Jack's three-year undercover assignment with John's estrangement from his son. The film says Jack's operation lasted three years; it does not give the same precise duration for how long father and son had been out of contact.