If Little Light started reading 80 pages a day from January 5th, he would need to finish 1/8 of the novel on the 10th day. Therefore, Little Light needed to finish reading the novel on January 12th. If Little Light read 90 pages a day, he would need 16 days to finish 1/8 of the novel, which was 120 pages. Therefore, Little Light needed to finish reading the novel on January 16th.