[pygtk] Sorting dates in a liststore

[Timo]

In my program, the user can enter a date in a entry (and some other data 
too) and it'll append in a liststore/treeview.
I'm having problems sorting this date column. Since notations of dates 
are different around the world ( dd/mm/yyyy, mm/dd/yy, dd-mm/yy, etc.), 
how can this be done?
Do I have to replace the entry with 3 spinbuttons perhaps? But how can I 
put them all in one column together, and to be sortable?