Hi,

XmlDateTime will write out up to 9 fractional second digits, but does not write out trailing 0's as per the XML Schema specification:
https://www.w3.org/TR/xmlschema-2/#dateTime

Section 3.2.7.2 Canonical representation:
- The fractional second string, if present, must not end in '0';

If you want a non-conforming date format then you can simply change the XSD to use an xs:string instead of an xs:dateTime and set whatever value you like. You could also specifying a Pattern facet on the xs:string to restrict valid values.