Year 503 (DIII) was a common year starting on Wednesday (link will display the full calendar) of the Julian calendar. At the time, it was known as the Year of the Consulship of Volusianus and Dixicrates (or, less frequently, year 1256 Ab urbe condita). The denomination 503 for this year has been used since the early medieval period, when the Anno Domini calendar era became the prevalent method in Europe for naming years.
An error (from the Latin error, meaning "wandering") is an action which is inaccurate or incorrect. In some usages, an error is synonymous with a mistake. In statistics, "error" refers to the difference between the value which has been computed and the correct value. An error could result in failure or in a deviation from the intended performance or behaviour.