'Old' in the Bible

(Saul's son Ish-bosheth was forty years old when he became king over Israel, and he was ruler for two years.) But Judah was on the side of David.

Now Jonathan, Saul's son, had a son whose feet were damaged. He was five years old when news of the death of Saul and Jonathan came from Jezreel, and the woman who took care of him took him up and went in flight: and while she was getting him away as quickly as she was able, he had a fall and his feet were damaged. His name was Mephibosheth.

David was thirty years old when he became king, and he was king for forty years,

Now Barzillai was a very old man, as much as eighty years old: and he had given the king everything he had need of, while he was at Mahanaim, for he was a very great man.

I am now eighty years old: good and bad are the same to me; have meat and drink any taste for me now? am I able to take pleasure in the voices of men or women in song? why then am I to be a trouble to my lord the king?

Then she said, In the old days, there was a saying, Let them put the question in Abel and in Dan, saying, Has what was ordered by men of good faith in Israel ever come to an end?