structural:expansion
Measures, calendrics and mathematics

Inca calendars were strongly tied to astronomy. Inca astronomers understood equinoxes, solstices and zenith passages, along with the Venus cycle. They could not, however, predict eclipses. The Inca calendar was essentially lunisolar, as two calendars were maintained in parallel, one solar and one lunar. As 12 lunar months fall 11 days short of a full 365-day solar year, those in charge of the calendar had to adjust every winter solstice. Each lunar month was marked with festivals and rituals. Apparently, the days of the week were not named and days were not grouped into weeks. Similarly, months were not grouped into seasons. Time during a day was not measured in hours or minutes, but in terms of how far the sun had travelled or in how long it had taken to perform a task.