During what period was the schedule invented?
In what period did the timetable initially developed?
In what period did the schedule emerge?
In which period did the schedule initially devised?
In which period was the agenda originally envisioned?
At what time did the timetable firstly introduced?
In what period was the timetable generation?
At what time was the agenda emerge for the first time?
Exploring the history and evolution of Advent calendars NPR