>What verses are you looking at?
Well, for point A, about the time of the last supper in the Synoptics, I would point to Mark 14:12
>And the first day of unleavened bread, when they killed the passover, his disciples said unto him, Where wilt thou that we go and prepare that thou mayest eat the passover
Matthew 26:17
>Now the first day of the feast of unleavened bread the disciples came to Jesus, saying unto him, Where wilt thou that we prepare for thee to eat the passover?
And Luke 22:7-8
>7 Then came the day of unleavened bread, when the passover must be killed.
>8 And he sent Peter and John, saying, Go and prepare us the passover, that we may eat.
All three have them very cognizant that this night's supper will include the Paschal lamb, necessitating that the last supper be after the bringing of said lamb.
For point B, that John doesn't see things that way, I'd look at 18:28 for starters
> Then led they Jesus from Caiaphas unto the hall of judgment: and it was early; and they themselves went not into the judgment hall, lest they should be defiled; but that they might eat the passover.
This would be after his arrest and trial before Ciaphas, which is of course necessarily after the Last Supper, which means that John thinks it's on a different day than Mark, Matthew, and Luke.