Although tradition says that Peter was crucified on the orders of Emperor Nero, it seems that this was unlikely to have been the case. In fact we do not know when or how Peter really died.
The first known mention of the execution of St. Peter was made by the second-century Pope Anicetus who, wishing to demonstrate that he spoke with the authority of Peter, reported that Peter had been beheaded in Rome. A century later, Origen changed this to say that Peter was sentenced to crucifixion but, feeling unworthy of being crucified like Jesus, asked to be crucified upside down.
Yet Clement of Rome, writing around 95 CE (1 Clement), spoke in general terms about the life and death of Peter but appears to have been unaware that he had even visited Rome and was certainly unaware that he had been executed in any way at all.
Another answer from our community:
Nero died in 68AD and tradition says Peter died in Nero's persecution. It is believed that it was about 67-68AD when Nero had Peter crucified.
He died on the cross upside down as he wished.
His date of birth is unknown. The date of his death is indicated as 64 AD.
He was crucified upside-down in A.D 64.
Peter was 64 when Jesus died
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