New Chronicles of Rebecca by Kate Douglas Wiggin

Even when Rebecca had left school, having attained the great age of seventeen and therefore able to look back over a past incredibly long and full, she still reckoned time not by years, but by certain important occurrences.

There was the year her father died; the year she left Sunnybrook Farm to come to her aunts in Riverboro; the year Sister Hannah became engaged; the year little Mira died; the year Abijah Flagg ceased to be Squire Bean's chore-boy, and astounded Riverboro by departing for Limerick Academy in search of an education; and finally the year of her graduation, which, to the mind of seventeen, seems rather the culmination than the beginning of existence.