Roman emperor Hadrian adopted Antoninus Pius as his son and successor following the death of Hadrian's first adopted son Lucius Aelius. AD 138: Year 138 (CXXXVIII) was a common year starting on Tuesday of the Julian calendar. At the time, it was known as the Year of the Consulship of Niger and Camerinus. The denomination 138 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. February 25, 138. Wiki link