The writer said that the era in which the events recorded took place was during the period when the judges governed Israel (1:1). Many students of the book have concluded that the genealogy in 4:18-22 helps to identify when during this period Ruth lived. If the genealogy is complete, Boaz lived during the seventh generation after Perez, the son of Judah, and Boaz was King David's great-grandfather. Life spans during the patriarchal period were sometimes very long, so it may be safer to calculate back from David. Conservative dates for David's lifetime are about 1041-971 B.C.4David was the seventh son born to his father (1 Chron. 2:15) who may have been born 35 years or more earlier. Boaz might have been born about 1150 B.C. and his son, Obed, by Ruth about 1100 B.C. Since most of the events recorded in Ruth took place shortly before Obed's birth we might conclude that these events happened around 1100 B.C. This would place Ruth in Israel during the judgeship of Samson (c. 1105-1085 B.C.) and the ministry of Samuel (c. 1115-1021 B.C.).5
The problem with these calculations is that four biblical genealogies also list Boaz as the son of Salmon, the husband of Rahab the harlot (Ruth 4:21; 1 Chron. 2:11; Matt. 1:5; Luke 3:32). Rahab was an adult when the conquest of the Promised Land began (c. 1406 B.C.). Boaz then may have been born shortly after that.6This would mean that the three generations of Boaz, his son Obed, and his grandson Jesse covered about 360 years (c. 1400-1040 B.C.). This seems quite impossible.
Probably these genealogies are incomplete and record only the names of outstanding individuals in David's family tree.7Consequently exactly when within the period of the judges the events of Ruth occurred remains a mystery.
"The Book of Ruth is a pearl in the swine pen of the judges."8