When did Jesus Christ make the time of Peter's death clear to him?

We are not told when the Lord revealed to Peter that his death was near. The Greek can be translated as also rather than simply as, suggesting that there might be evidence from other sources that his death was approaching. For one, Peter would have been close to the age of sixty in a time when the average life span was around forty years or less. Additionally, if Peter wrote his letter around 68 AD, he also wrote in a time where there was anti-Christian violence in Rome on account of Emperor Nero.¹ In the Gospel of John, we are also told that the Lord Jesus made a prediction about Peter’s death (John 21:18–19) though it is not clear how this would have helped Peter to know when the time was near. Perhaps he had a special vision from Christ that has not been recorded in Scripture.² According to church tradition, Peter died as a martyr in Rome, hung upside down on a cross (Eusebius, Ecclesiastical History, 3.1.2).