According to the federal system, prisoners who have demonstrated “exemplary compliance with institutional disciplinary regulations” can get up to 54 days per year off their sentences! Meaning they will get out of jail earlier than their assigned sentence. (18 U.S. Code § 3624(b)). American prisons have been letting out well-behaved inmates early since 1817.
Jail and Prison are two terms that are often interchanged and used as one. While it's not widely known, jail and prison are actually two different places and have completely different meanings. The jail system is managed by the state, and prisons are a separate federal entity, governed by the federal government. In order to get into prison, you would have to have been given a sentence longer than 1 year. Prison is also for more serious crimes such as felonies, whereas jail is mostly used for misdemeanors.
While being sent to jail is vastly different from receiving a prison sentence, in jail, the person who committed the crime has the opportunity to get out of jail early, so to speak. This however would depend on the inmate showing good behavior. You can be given time off your original sentence in both the prison, and the jail system.
An inmate can get 54 days off their sentence per year served for good behavior. This means that someone who's serving 13 months in jail, wouldn't be allowed out 54 days early during their 11th month. But instead, they would only become eligible to have time off their sentence after they had served a full 12 month period.
Almost all prisoners are eligible for a reduction to their sentence using the rule above that allows 54 days to be reduced on their sentence per each year they serve in prison. However, there is an exception to this rule; when a prisoner has been convicted of a crime so serious that they've been sentenced to life in prison, or death row, they will unfortunately become ineligible for any kind of reduction to their sentence.
The amount of time off any sentence varies greatly from inmate to inmate. One could be just a few days off, while others could have several months of reduced jail time. The better and more consistent an inmate is with their good behavior will determine how much time off each person receives. To get out of jail early is all well and good. But can inmates stay longer for poor behavior? The answer to this is no, your sentence can not be extended without a new trial. For this reason, inmates cannot legally be held longer than their original verdict.
Parole is when inmates are released from Prison temporarily or permanently from their good behavior. When they are released, they are called a parolee, and they are allowed to live the rest of their sentence in the outside world as long as they are following the rules and keeping up their good behavior.
Parole is not a right, it’s an opportunity, and it isn’t given to everyone; in fact, it is only given to a few people. Parolees are watched diligently by parole officers with whom they're required to check in on a weekly basis. Each probation officer will give their parolee a strict set of rules to follow and if any rules are broken during the probation period, the parolee will be returned to prison for the duration of their sentence. Knowing this, many parolees are very careful to continue their good behavior and become law-abiding citizens outside of prison to maintain their freedom.
Inmates will often see the benefits of showing off their good behavior in prison. Good behavior can include everyday activities like making their bed in the morning, showing up for the head count, and keeping bodily fluids contained to themselves. All this in addition to avoiding any behaviors that are prohibited in prison. Prisoners who do have good behavior results in a much nicer living environment for the rest of their neighboring inmates.