Message

A Date MUST have timezone and a granularity of seconds.

Context
query:QueryResponse/rim:Slot[@name='IssueDateTime']/rim:SlotValue/rim:Value
Test
./text()[matches(normalize-space(),'^([0-9]{4}-(0[1-9]|1[0-2])-(0[1-9]|[12][0-9]|3[01]))T(([01][0-9]|2[0-3]):[0-5][0-9]:[0-5][0-9]|(24:00:00))(Z|(\+|-)((0[0-9]|1[0-3]):[0-5][0-9]|14:00))$')]
Usage
/ query:QueryResponse / rim:Slot@name=IssueDateTime / rim:SlotValue / rim:Value