When did the calendar devised?
In what period did the schedule first devised?
At what time was the timetable emerge?
In which period was the schedule originally invented?
During what period was the timetable originally imagined?
During what period was the schedule firstly introduced?
In which period was the timetable generation?
In which period was the calendar come about for the first time?
When Was the Calendar Invented A Look at the History and