The dateTime data type represents a specific time and date : dateTime « XML Schema « XML Tutorial

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3. dateTime

<!-- schema -->
<xsd:element name="time_of_birth">
  <xsd:simpleType>
   <xsd:restriction base="xsd:dateTime">
    <xsd:enumeration value="1950-06-25T04:15:00"/>
    <xsd:enumeration value="1988-12-14T21:30:05"/>
   </xsd:restriction>
  </xsd:simpleType>
</xsd:element>
<!-- instance document -->
<time_of_birth>1950-06-25T04:15:00</time_of_birth>