In Time

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In 2169, people are genetically engineered with perfect health and appearance. Each has a digital clock on their forearm; when they turn 25, they stop aging and their clock begins counting down from 1 year.[Note 1] When the clock reaches zero, that person "times out" and dies. Time has become the universal currency, and can be transferred between people or "time capsules". The film focuses on two specific "time zones": Dayton - a poor manufacturing area where people generally have 24 hours or less on their clock at any given time - and New Greenwich - the wealthiest time zone, where people have enough time on their clock to live for centuries.
Will Salas is a 28-year-old Dayton factory worker living with his 50-year-old mother Rachel. He saves a drunken 105-year-old man named Henry Hamilton from an attempted robbery by a gang of "Minutemen" (time-robbing thugs) led by 75-year-old Fortis. Hamilton reveals to Will that the people of New Greenwich hoard most of the time for themselves to live forever, while constantly increasing the cost of living keeps poorer people dying. The next morning, Hamilton transfers 116 years of his time to a sleeping Will, before timing out and falling off a bridge. Raymond Leon, leader of the police-like Timekeepers erroneously assumes that Will played a part in Hamilton's death.
Will visits his best friend Borel and tells him of the time he received. Borel warns him that having so much time within Dayton will get him killed. Will gives Borel ten years in return for their years of friendship before going to wait for his mother so they can move to New Greewich. Rachel uses all but 90 minutes of her time to pay off a 2-day loan and finds herself short for bus fare to get home. She urges the bus driver to lend her a loan of 30 minutes that her son will pay off but to which he refuses and advises her to run. She times out in Will's arms before they can reach each other and Will can lend her time.
The following morning, Will heads to New Greenwich. He visits a local casino and meets 110-year-old time-loaning businessman Philippe Weis and his 27-year-old daughter Sylvia. While playing poker with Weis, Will comes dangerously close to timing out, but eventually wins 1,100 years. Sylvia invites him to a party in the Weis mansion. Will buys a car and drives himself to the party, where the Timekeepers arrest him.
Dismissing Will's claim of innocence, Raymond confiscates all but two hours of his time. Will takes Sylvia as hostage and drives back to Dayton. They are ambushed by Fortis' gang, and are left with 30 minutes each. Will attempts to get some time back from Borel, but his wife Greta tells him that he has drunk himself to death with nine years left on his clock. Sylvia pawns her jewelry for extra time, and Will calls Weis to demand a 1,000 year ransom. When Weis refuses to pay, Will decides to release Sylvia. She calls Weis from a pay phone, but they are ambushed by Raymond, whom Sylvia shoots by accident.
Will and Sylvia decide to team up and begin robbing Weis' time banks, giving the extra time capsules to the poor. After a ten-year reward is offered for their capture, Fortis' gang tracks them down to a hotel room. Will challenges Fortis to a "time-duel" to the death, in which he times out Fortis by applying his father's time duel trick and shoots the rest of the gang. However, the pair realize they cannot steal enough time to significantly change things, as New Greenwich simply raises prices to compensate for the extra time citizens now have.
They successfully rob Weis' personal vault and obtain the one-million-years capsule. Raymond chases them back to Dayton, but is too late to stop them from distributing the stolen time as Will distributes the time to the girl. After chasing them to the city's outskirts, Raymond reveals that he also came from Dayton and intends to stop other Daytoners from doing the same. However, he realizes too late that he forgot to collect his daily time allotment and times out. Will and Sylvia, each with just over a minute to live, race to Raymond's patrol car. Will collects Raymond's daily share and runs back to Sylvia in a scene reminiscent of his mother's death. This time, he saves her when her clock only has seconds left.
TV reports show factories in Dayton shutting down as everyone has enough time and abandons their jobs to go to New Greenwich. Will and Sylvia continue robbing banks as part of their efforts to crash the system, while the rich attempt to cope with the sudden surge of people infiltrating their zone.

Question: What age do people stop aging?
Answer: 25 years old.