Book 2 contains material on the distance between the earth and the heavens, and between the seven planets; methods for counting the lunar months; the monthly age of the moon; rules for calculating Easter and Lent; intercalary days (extra days) and subtracted days; solar and lunar years; more on versification.
Book 3 contains material on cycles of the stars; 19 year lunar cycles; other large cycles of the sun and moon; the first day of the natural year (the spring equinox in March).