When sentences run concurrently, defendants serve all the sentences at the same time. When sentences run consecutively, defendants have to finish serving the sentence for one offense before they start serving the sentence for any other offense. If a defendant is convicted of a number of crimes that carry lengthy prison terms, the difference between consecutive and concurrent sentences can be tremendous. The same factors that judges tend to consider when deciding on the severity of a sentence (for example, a defendant’s past record) also affect their decisions on whether to give concurrent or consecutive sentences. Some criminal statutes, however, require that the sentence for the crime in question be served consecutively to any other crime committed in the same incident. Sentence days are ANY days of incarceration, even if only for an hour, it counts as one day.