A more thorough explanation:

Definition: Commission day is the first day of the assizes in English law. It is the day when the commission that gives the judge the authority to act is publicly read.

Example: The commission day is an important day in the legal calendar of England. It marks the beginning of the assizes, which are held twice a year in each county. On this day, the judge is officially authorized to hear cases and make judgments.

Explanation: The example illustrates how commission day is the first day of the assizes and how it is an important day in the legal system of England. It also shows how the commission that authorizes the judge to act is publicly read on this day, giving the judge the authority to hear cases and make judgments.