"I don't have time. I don't have time to worry about how it happened. It is what it is. We're genetically engineered to stop aging at 25. The trouble is, we live only one more year, unless we can get more time. Time is now the currency. We earn it and spend it. The rich can live forever. And the rest of us? I just want to wake up with more time on my hands than hours in the day" -- Will Salas (Justin Timberlake) In Time 
These are the opening lines to the film In Time where time literally is money. At age 25 you stop aging, but you only have one year left to live. You can work for more time, trade time, steal time and fight for time, no matter what you spend time.
A phone call costs one minute of your life, a ride on the bus is two hours. Some have millions of years in their bank; they will live forever; as long as they don't have an accident. Some like Will Salas (Justin Timberlake) live almost down to the wire, sometimes only having seconds left before they earn and load more time, often no more than a day at a time. Run out of time and your heart just shuts down. You literally die in your tracks.
In Time  has a very basic plot. A very rich man who is tired of living gives Will 100 years of life, and then uses his last seconds to watch the sunrise and die. The Time Police believe Will stole the time, take back all but a day and put him on trial. Will escapes and takes Sylvia Weis (Amanda Seyfried), the daughter of the richest man in the city, hostage and goes on the run. You can predict the rest easily if you want to, but you don't watch this movie only for the story but for the workings of a world where time is money.