A more thorough explanation:

A calendar of prisoners is a historical document that contains a list of all the prisoners in custody. It is kept by the sheriffs and includes notes about each prisoner's present and past convictions.

For example, in the 18th century, the sheriff of a county would keep a calendar of prisoners in a physical book. The book would contain the names of all the prisoners in custody, along with information about their crimes and sentences.

Today, the term "calendar of prisoners" is still used in some legal systems to refer to a list of all the prisoners who are due to appear in court on a particular day.

Overall, a calendar of prisoners is an important tool for law enforcement officials to keep track of the individuals in their custody and to ensure that justice is served.