Anthony Aveni asserts, "Once a Maya genius may have recognized that somewhere deep within the calendar system lay the miraculous union, the magical crossing point of a host of time cycles: 9 moons, 13 times 20, a birth cycle, a planting cycle, a Venus cycle, a sun cycle, an eclipse cycle. The number 260 was tailor made for the Maya". Others have observed that the "Venus Table" in the Dresden Codex, is an accurate ephemeris for predicting Venus positions. Others have also observed a basis for the 260-day cycle in the agricultural cycle of highland Guatemala, which is also about 260 days. Aveni notes that "the average duration between successive halves of the eclipse season, at 173 ½ days, fits into the tzolkin in the ratio of 3 to 2." This may seem contrived, but the Maya did employ the tzolkin to predict positions of Venus and eclipses.