Now you might notice that there is a difference between Luke's reckoning and Matthew's and Mark's reckoning. Matthew and Mark say six days. Luke says eight days. The only difference is the time or the point from which they begin to count. Matthew's and Mark's took place six days after the things that He said that included, Get behind Me, Satan! Luke included all of the events of chapter 16, which took a couple of days to unfold. And so his is naturally then, longer, eight days rather than six days.
Why did they go up to the mountain to pray?