'Generation' in the Bible

Now David, having done God's work for his generation, went to sleep, and was put with his fathers, and his body came to destruction:

And I went farther in the Jews' religion than a number of my generation among my countrymen, having a more burning interest in the beliefs handed down from my fathers.

So that you may be holy and gentle, children of God without sin in a twisted and foolish generation, among whom you are seen as lights in the world,

So that I was angry with this generation, and I said, Their hearts are in error at all times, and they have no knowledge of my ways;