Autumn has been used for centuries as a symbol for middle age, decline and fatigue. When Yeats writes, "The trees are in their autumn beauty. . ." he is setting up an atmosphere of a change between the time of summer's beauty and the coldness and death of winter. The poem was first written in 1916, when Yeats was 51 years old. He was not married and had no children and he was beginning to think that "life had passed him by". Thus, Yeats is setting up a contrast between his own life, which he considers to be now like autumn. He says, "All's changed" and his heart " has grown old." However, the swans, representing nature and life, are still "unwearied" and seem to have lots of energy. Autumn represents Yeats' depressed feeling about life at the time he wrote the poem. Fortunately, Yeats did marry later on and had two children.