I completely agree with you and, from a brief look at the discussion boards, it seems as though changing to a Monday-Sunday calendar view in Week and Month views is not possible in iOS without changing region setting in International to Barbados or something similar without changing languages. It used to be possible to switch to the UK or Australia for this, but that has changed with iOS6. However, the problem with changing regions to non-US or -UK is that it turns off turn-by-turn directions in Maps. Apple needs to add a setting directly to Calendar in iOS. Note that changing the setting in iCloud doesn't translate to a change on one's iPhone or iPad. Infuriating!