The passage of time plays a crucial and constant role throughout Dragon Ball, to the point one could successfully argue that it’s one of the story’s natural themes. The series chronicles roughly three decades of Son Goku’s life and that time can very much be felt. Characters come and go, ideals change, and the status quo is shaken up for more often than fans give the story credit. Dragon Ball Z owes so much of its narrative and thematic weight to the fact that it allows time to pass.
Source：https://www.cbr.com/dragon-ball-anime-every-time-skip-chronological-order/
