"And he said unto them, Verily I say unto you, That there be some of them that stand here, which shall not taste of death, till they have seen the kingdom of God come with power." (Mark 9: 1)
Few understand that this prophecy was fulfilled six days after it was given.
This is because the Kingdom of God exists outside of time as we experience it: in the Kingdom, past and future can be at once present. Sometimes, in the course of history, individuals have been allowed to step outside of time to see the way the Kingdom appears when all times are allowed to co-exist. When the kingdom of God comes to earth in its power, human time will melt away as the hoar frost before the sun. In isolated instances, however, individuals have already passed through the constraints of human time, even in their mortality, to experience the time of the Kingdom. This, too, is a coming of the Kingdom of God in power.
One of these instances was at the valley of Adam-ondi-Ahman: when Adam gathered his posterity to bless them, the godliness with him was so great that the future also became present and he was able to bless the whole of his posterity though all the generations and dispensations that would come to exist on earth. We have yet to live the same moment he lived then, but before the Savior returns, the godliness with us will be so great that we will see our presence before Adam and the dispensations of the gospel will melt together. What happened near to the beginning of earth's time and what will happen toward the end of earth's time are in fact as one moment in the Kingdom, simply viewed through two different angles.
Enoch and the people of Zion, likewise, stepped out of time, but so fully that they only become present in human time when others match their righteousness and are able to experience the omnipresent time of the Kingdom with them. This is the way in which Enoch's Zion will join our Zion in the last days: as soon as we can see time as God does, we will see that we are standing in their presence.
Six days after prophesying that some would see the Kingdom before tasting death, Jesus took Peter, James and John to a high mountain. That they saw Christ glorified there could happen because they had been allowed to step out of time and into the Kingdom, where the future, glorified Christ was already present. They also saw Elias and Moses from the past--on the mountain, Moses had once seen them as he received the commandments including the Melchizedek Priesthood!
It is said that in the temples, the human time grows particularly porous. It is through our presence in the temples that we are prepared to step out of human time.