DBT, you are confusing 2 different prophecies given about 6 months apart. The fulfillment of the 2nd one is still ahead.
Matthew 24, Mark 13, and Luke 21 describes the 2nd one which is to occur "at an hour you do not think it to be" - Matt 24:44
The transfiguration took place 6 days after Jesus said:
Truly I say to you that there are some of those standing here who will not taste death at all until first they see the Son of man coming in his Kingdom.” - Matt 16:28
