When describing the Spanish judiciary, there is a peculiar context in which the adjective moderno cannot be rendered as “modern,” and failure to recognize that fact could prove a source of serious translation mistakes. For example, the expression magistrado más moderno de la Sala Primera del Tribunal Supremo does not refer to the most modern or fashionable of the judges, but rather to the “judge with the least seniority in the Civil Division of the Supreme Court.”
“Seniority” is of course antigüedad, and magistrado más moderno denotes the judge with the least seniority (but not necessarily the youngest) on a given court or among a panel of judges, while magistrado más antiguo describes the judge with the most seniority (but not necessarily the oldest).
In Spain judges’ seniority is determined each year in the Escalafón de la Carrera Judicial (Career Judges Seniority Ranking), prepared by the Comisión Permanente del Consejo General del Poder Judicial (Standing Committee of the General Council of the Judiciary). And being the más moderno is significant in many instances. As an example (there are many others), regarding deliberations and voting to reach a decision and render judgment, the Ley Orgánica del Poder Judicial provides that concluida la discusión de cada asunto, se procederá a la votación, que comenzará por el Juez o Magistrado más moderno y seguirá por orden de menor antigüedad, hasta el que presidiere (Art. 157).