John places the feeding of the 5,000, Jesus walking on water, and the Bread of Life Discourse which follows at a time before Passover:
Now the Passover, the feast of the Jews, was at hand. (John 6:4) [ESV]
Many note the difficulty of this timing; calling the accuracy of the text and/or John's knowledge of Judaism into question. C.K. Barrett notes Hort's concerns:
The authenticity of these words was suspected by Hort, though they are contained in all MSS. and VSS. and the only evidence against them is patristic...Hort concludes "The supposition that τὸ πάσχα formed no part of the original text must remain somewhat precarious in the absence of any other apparent corruption of equal magnitude and similarly attested by all know MSS. and VSS. But as a considerable body of patristic evidence points to the absence of the words in at least some ancient texts, and the internal evidence is unfavourable to their genuineness, while the chronology of the gospel history is fundamentally affected by their presence or absence, it has seemed right to express suspicion, and to justify it at some length." 1
Israel Abrahams' analysis of the customs led him to conclude the Passover was past:
Everything points then, to a date soon after the Passover. 2
Under some circumstances the Passover could be celebrated on the 14th of the second month (Numbers 9:6-14). This is called Pesach Sheni. The objections, such as the availability of barley loaves (6:9) and the people not being in Jerusalem are resolved if John is referring to the second month Passover. Also, the chronology and period of time the Gospel covers would be unchanged.
In the Bread of Life Discourse there is a comparison with the manna which fell for 40 years in the wilderness. It begins with:
So they said to him, “Then what sign do you do, that we may see and believe you? What work do you perform? Our fathers ate the manna in the wilderness; as it is written, ‘He gave them bread from heaven to eat.’” (John 6:31-32)
Interestingly, a connection between the manna and the second month Passover exists:
...on the fifteenth day of the second month after they had departed from the land of Egypt. And the whole congregation of the people of Israel grumbled against Moses and Aaron in the wilderness...So Moses and Aaron said to all the people of Israel, “At evening you shall know that it was the LORD who brought you out of the land of Egypt, and in the morning you shall see the glory of the LORD... (Exodus 16:1-2, 6-7)
Once Pesach Sheni is established, a "remembrance" of when the manna begin to fall would come soon after. If John were writing after the destruction of Jerusalem, he could reasonably call the 14th day of the second month as "the Passover of the Jews."
Has John retrospectively recognized the Bread of Life Discourse took place at the time of Pesach Sheni?
1. C.K. Barrett, The Gospel According to St. John, S.P.C.K, 1962, p. 228
2. Abrahams, Studies in Pharisaism and the Gospels, Cambridge University Press, 1917, p. 11