“a Sabbath of complete rest.” The Hebrew is shabbath shabbathon, more literally, “a Sabbath of Sabbath observance.” For more information, see commentary on Leviticus 25:4.

“In the ninth day of the month at evening, from evening to evening.” Sunset on the ninth day of the month Tishri started the tenth day of Tishri and the Day of Atonement (Yom Kippur), which went to sunset the next day. Thus the Day of Atonement went from sunset on the ninth of Tishri to sunset on the tenth of Tishri, one full 24-hour day.