When can we start...............................?

"Whatever one's religion...walking the labyrinth clears the mind and gives insight.   It calms people in the throes of life's transitions."    
I'd bet the same would be true if you just traced the path (a non-sceptical attitude might help) with the point of a pencil.  More information about The Sacred Labyrinth Walk is here.  More information specifically about The Chartres Labyrinth can be found here.  The Cliff Notes on the Chartres Cathedral are here.  Enjoy!