Because time is not like space. And when you put something down somewhere, like a protractor or a biscuit, you can have a map in your head to tell you where you have left it, but even if you don't have a map it will still be there because a map is a representation of things that actually exist so you can find the protractor or the biscuits again. And a timetable is a map of time, except that if you don't have a timetable, time isn't there like the landing and the garden and the route to school.
Mark Haddon, The Curious Incident of the Dog in the Night-Time
space, time