沧海桑田 （沧桑） seas change into mulberry fields ——time brings great changes to the world.

天若有情天亦老，人间正道是沧桑。语出毛泽东诗词。

Were nature sentient, she too would pass from youth to age. But Man's world is mutable, seas become muberry fields. (Mao Zedong's poem)

饱经沧桑 have experienced many vicissitudes of life