In which period did the timetable originated?
During what period was the timetable first established?
In which period did the calendar arise?
At what time was the calendar firstly created?
In which period did the agenda initially thought up?
At what time did the agenda initially established?
At what time was the schedule creation?
In which period was the schedule come about for the first time?
Counting down to Christmas A history of the Advent Calendar
