What does the speaker realize by the end of "because I could not stop for death"?

By the end of the poem "because I could not stop for death", the speaker realises that all the centuries which have been passed feels shorter than the day. The day in which she imagines of nearing to death, that day is much longer than her entire life. She took the fateful ride through carriage and that felt to her as the longest journey. The time which she spent gave her the idea and the truest meaning of immortality.