The quatrefoil frame at the bottom of the March calendar page contains the zodiacal emblem of Aries, a ram. In his Etymologiae, the encyclopedist St. Isidore says that Aries is thus named because of Jupiter Ammon, who was depicted with ram???s horns. The thirteenth-century Breviari d???amor provides a novel explanation for an ancient association: just as the ram sleeps on both his sides, so the sun is equal in relation to the earth on both sides in the sign of Aries. The vernal equinox occurs in this sign (Teresa P??rez-Higuera, Medieval Calendars, 1997).