user update date field wrong

Good day,

I have two forms in user registration (1.5 beta 1.8): “register” and “update registration”. There is a field “birth date” in both forms (date picker, dd-mm-yyyy – 16-06-2000).
When I open the update form for a user, the field value of the birth date comes out wrongly: mm-dd-yyyy (06-16-2000) while the date picker has dd-mm-yyyy (16-06-2000).
Because it sees the day value now as month value, it won’t update (there is no month beyond December).
Did I oversee something? Help would be apreciated.

Albert