Pope Anicetus was the bishop of Rome from around 157 to his death in April 168. Anicetus actively opposed Gnosticism and Marcionism. He welcomed Polycarp of Smyrna to Rome to discuss the Easter date controversy.
Anicetus was a Syrian from the city of Emesa, now known as Homs. According to Irenaeus, it was during his pontificate that the aged Polycarp of Smyrna, a disciple of John the Evangelist, visited Rome to discuss the celebration of Easter with Anicetus. Polycarp and his Church of Smyrna celebrated the crucifixion on the fourteenth day of Nisan, which coincides with Passover regardless of which day of the week upon this date fell, while the Roman Church celebrated Easter on Sunday—the weekday of Jesus’s resurrection. The two did not agree on a common date, but Anicetus conceded to Polycarp and the Church of Smyrna the ability to keep the date they had been using. The disagreement would get heated in the following centuries.
Papal records show Anicetus decreed that priests are not allowed to have long hair, perhaps because the Gnostics wore long hair.
According to church tradition, Anicetus suffered martyrdom during the reign of Emperor Lucius Verus, but there are no historical records from this time. April 16, 17, and 20 April are all cited as the date of his death, but 20 April is currently celebrated as his feast day.