Drusilla, Caligula's sister who died in June, with whom the emperor is said to have an incestuous relationship, is deified.

AD 38 (XXXVIII) was a common year starting on Wednesday of the Julian calendar. At the time, it was known as the Year of the Consulship of Iulianus and Asprenas. The denomination AD 38 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.

Julia Drusilla was a member of the Roman imperial family, the second daughter and fifth child of Germanicus and Agrippina the Elder to survive infancy. She was the favorite sister of Emperor Caligula, who, after her death, had her deified under the name Diva Drusilla Panthea, and named his daughter Julia Drusilla after her.

Gaius Caesar Augustus Germanicus, also called Gaius and Caligula, was Roman emperor from AD 37 until his assassination in 41. He was the son of the Roman general Germanicus and Augustus' granddaughter Agrippina the Elder, members of the first ruling family of the Roman Empire. He was born two years before Tiberius became emperor. Gaius accompanied his father, mother and siblings on campaign in Germania, at little more than four or five years old. He had been named after Gaius Julius Caesar, but his father's soldiers affectionately nicknamed him "Caligula".

September 23 is the 266th day of the year in the Gregorian calendar; 99 days remain until the end of the year.