Analysis of the iconography in a directional almanac on Codex Borgia pages 49–52 invites comparison with almanacs in a related set of divinatory manuscripts known as the Borgia Group, but one aspect of the Codex Borgia almanac remains unique. It records real-time dates employing the central Mexican system of year dates that help identify the images as year-end rituals. These fifteenth-century dates correlate with the last twenty-day “month” in the year, known as Izcalli in the Valley of Mexico and neighboring Tlaxcala. Izcalli rituals in February involved drilling a new fire, the erection of sacred trees, and animal sacrifice, all of which appear on Borgia 49–52. During Izcalli, human sacrifice was performed only every fourth year, a pattern like that seen in the Codex Borgia and the Codex Cospi, where death imagery and decapitated humans appear prominently on the fourth year-bearer page, associated with the southern direction. Borgia Group codices also depict trees and birds representing the four cardinal directions. These are most prominent on Codex Fejérváry-Mayer page 1 in a cosmogram representing two different calendar formats, like those seen in the Borgia almanac. The 5 × 52-day format was used to measure the solar year and Venus cycle, and a second set of day signs appears in a 4 × 65-day pattern useful in calculating the fifty-two-year cycle and the Venus cycle. This provides a subtext for understanding the dates represented on Borgia 49–52 and the extension of the almanac on page 53, where the Venus almanac begins.
The new Athens center on data processing from the neutron monitor network in real time