In which period was the calendar invented?
During what period was the calendar initially developed?
In which period was the calendar come into existence?
During what period did the agenda originally created?
In which period was the timetable firstly thought up?
At what time did the calendar firstly established?
In which period
did the calendar generation?
When was the schedule arise for the first time?
Mesoamericans Have Been Using a 260Day Ceremonial Calendar