Recently I had to made proper formatting of NotesDateTime object (using LotusScript) with respect to different locale. I had written a cover in LS2J for Java SimpleDateFormat class that works independently (without Java library), so copy/paste and go on. Here is an example how it works.
This is a companion discussion topic for the original entry at http://dpastov.blogspot.com/2019/09/formatting-notesdatetime-as-java.html