Intervals of 260 days are recorded by architectural orientations at a number of Maya sites, a pattern that may have developed early at sites such as Nakbe. The 260-day calendar, emphasizing sets of 13 and 20 days, dates back to the Middle Preclassic, when early E-Groups in the Maya area were used for solar observations. These observations were probably linked with a maize cycle spanning 260 days. By the end of the Late Preclassic, however, most E-Groups were abandoned or modified for a different function, serving as a stage for rituals performed by rulers at a time when the Long Count calendar was being developed. The changing role of E-Groups relates to the rise of royal rituals associated with the detailed historical records documented in Maya Long Count inscriptions.