You can do it by using XPath, take a look:
http://www.w3.org/TR/xpath-functions/#dt-dayTimeDuration[
^]
10.3.2 xs:dayTimeDuration
[Definition] xs:dayTimeDuration is derived from xs:duration by restricting its lexical representation to contain only the days, hours, minutes and seconds components. The value space of xs:dayTimeDuration is the set of fractional second values. The components of xs:dayTimeDuration correspond to the day, hour, minute and second components defined in Section 5.5.3.2 of [ISO 8601], respectively.