As Leslie pointed out, date fields are actually stored as a number, so it doesn't matter what format you see the date as in your reports, forms, queries, etc.
If somebody's regional settings were "mm/dd/yyyy" and they entered "01/02/2007", and assuming there were no input masks, the date would be interpreted as January 2, 2007. If the regional settings were "dd/mm/yyyy", the date would be interpreted as February 1, 2007. But either way, the value being stored in the database is not "01/02/2007", it is some number like 38928.
So reading the first two characters doesn't help you, because what you are reading is the date after it's been converted back to a human-readable format. It does not tell you how the person entered the date in the first place. If their regional settings were "mm/dd/yyyy" they would see "01/02/2007", if my settings were "dd/mm/yyyy", I would see "02/01/2007", but in both cases the date is actually January 2, 2007.