In what period did the schedule created?
During what period was the agenda initially introduced?
In which period did the timetable arise?
At what time was the agenda firstly created?
During what period was the calendar initially imagined?
At what time was the timetable firstly devised?
During what period did the calendar generation?
In what period did the timetable emerge for the first time?
The Maya Calendar System Smithsonian Institution