Monica’s Zodiac Drawings – are somewhat whimsical depictions of each of the twelve celestial periods as devised by Babylonian astronomers during the early first millennium BC. These 5×7 prints in 8×10 matts make great birthday gifts.

Interesting facts from Wikipedia

The zodiac is the circle of twelve 30° divisions of celestial longitude employed by western astrology and (formerly) astronomy. The western zodiac is centered upon the ecliptic, the apparent path of the Sun across the celestial sphere over the course of the year. The paths of the Moon and visible planets also remain close to the ecliptic, within the belt of the zodiac, which extends 8-9° north or south of the ecliptic, as measured in celestial latitude. Because the divisions are regular, they do not correspond exactly to the boundaries of the twelve constellations after which they are named.

Historically, these twelve divisions are called signs. Essentially, the zodiac is a celestial coordinate system, or more specifically an ecliptic coordinate system, which takes the ecliptic as the origin of latitude, and the position of the Sun at vernal equinox as the origin of longitude.