I'd like to expand upon the other answer to this question by looking at time's power to outlast human life in the famous "Time Passes" section. Here, Woolf focuses on how the passage of time affects the Ramsay summer home when its primary inhabitants are gone. Lasting a period of roughly a decade (or, at the very least, a number of years which include the outbreak of the First World War and the subsequent armistice four years later), "Time Passes" witnesses the gradual decay of the Ramsay house.
Abandoned by the Ramsay family, the house is slowly reclaimed by nature, with birds and toads nesting in the woodwork and weeds and wild grasses taking over first the garden, then the interior. During this time, Woolf seems to more or less forget about her main characters, relegating their activities to condensed bracketed paragraphs, despite the fact that these activities would normally take up a large portion of any conventional narrative—Andrew and Mrs. Ramsay, for instance, die all of a sudden, despite the fact that they were major characters in the first section of the book.
In "Time Passes," therefore, it's useful to think of time as a main character in and of itself, a force of nature that takes center stage and reduces the human characters of the novel to footnotes. From the perspective of time, human activities occur in the mere blink of an eye and are barely worth registering, while the fruits of their labor (i.e., the Ramsay summer home and the coherent community it represents) can be destroyed without any special effort. Thus, in To the Lighthouse time becomes a force that is terrifying, not because it has any animosity toward humans, but rather because human beings are entirely inconsequential and meaningless in comparison to the inevitable progression of days and months and years. It's a haunting idea, one that Lily Briscoe will grapple with at length in the novel's third and final section.