Date of Birth during signup shows incorrect date

I'd set up half a dozen staff members iTunes account on their new iPads and found I had an issue on some of them where selecting the day of the month using the scroll-wheel would display the date incorrectly by one day. Eg selecting 29th of a month in a year would result in the DOB of 30/month/year. Makes no difference if the iPad is connected by iPhone tether or WiFi or 3G.

Just now same problem and managed to get some screen shots:

The time zone is selected and chosen prior to this step and I'm guessing the issue is possibly being caused by this. I can't recall if I had this problem when setting this up early AM for example. However NZ is gmt+12 (+13 during daylight savings) so If this were the case the day should be going backwards, not forwards ...