"And he spake to them a parable; Behold the fig tree, and all the trees;
When they now shoot forth, ye see and know of your own selves that summer is now nigh at hand.
So likewise ye, when ye see these things come to pass, know ye that the kingdom of God is nigh at hand.
Verily I say unto you, This generation shall not pass away, till all be fulfilled."
Luke 21:29-32

Many have thought that Jesus was talking about the generation immediately before them who saw His prophecy fulfilled in 70 A.D.

The word generation that comes from the Greek means family, race or people. Comparing this
meaning with others passages in the Bible, a generation could be a time period of 70 to 80 years.