datetime variation

Looking for a dateTime pattern variation,

<modified>2001-01-11T12:01:01Z</modified>
I.e. the normal xsd dateTime, but with a mandated Z,
as apposed to the +- alternatives.

Not working I have,

<element name="modified">
  <data type="dateTime">
         <param name="minInclusive">2000-01-01T00:00:00Z</param>
         <param name="maxInclusive">2099-12-31T23:59:59Z</param>
         <param 
name="pattern">[0-9]{4}-[0-9]{2}-[0-9]{2}T[0-9]2:[0-9]2:[0-9]2Z</param>
        </data>

  </element>

Ideally I'd like to split it up,
date,
T
time
Z
I can't find a way to do this.

1. Is this possible please?
2. If so, how?
3. If not... am I into defining my own library type?

TIA, DaveP