There's nothing worse than UI trying to do data validation...

The number of form validators that still barfs at anything that is not ACSCII7 isalpha() amazes me. Heck, the entire US is built by non-indigenous people! Internet domain names, HTTP 1.0 and HTML/2.0 since the RFC 2070 extension have mandated the support for unicode for almost 30 years - that's longer than the age of many professional developers.

Swedish social security numbers? Why do forms even allow the obsolete 2-digit year format after y2k?

Swedish postal codes have since 1968 by standard been written as 3 digits, space, 2 digits. I have rarely seen any system allowing a space - even UK postal codes requires space (and non-digits, too).

STOP VALIDATING USER INPUT unless there are strict INTERNATIONAL standarads explicitly EXCLUDING a specific format!