Are the holy men and women of the Old Testament, for example, Aaron, Moses, Daniel, David, Abraham, Samuel, Sarah, Rebecca, Ruth, etc., considered saints? Are feast days assigned to them and, if so, what days are they?
Some of the Old Testament names you mention can be found in The Book of Saints compiled by the Benedictine monks of St. Augustine’s, Ramsgate, published by Macmillan Company. Some of these names may also be found in lists of Christian names—without any notation of sanctity or a cult. In other dictionaries of the saints, there simply are no listings for these biblical figures.
At the same time, remember there was no formal process of canonization until 993. Earlier than that, people were accepted as saints by common opinion.
The Ramsgate book tells us of the feast days of Abraham (October 9), David (December 29), Moses (September 9) and Samuel (August 20), which are to be found listed in the Roman Martyrology. The Greeks celebrate a feast of David and all the ancestors of Jesus on December 19. Adam and Eve, December 24, are listed as having an approved cult.