timezone.xqy can convert between times in named timezones, using special TimeZoneInfo
files produced from UNIX zoneinfo files, e.g. it allows you to look up the equivalent time in New York, based on a time in London.
tz:adjust-dateTime-to-timezone(xs:dateTime('2013-05-09T10:34:00+01:00'),'America/New_York')
=> xs:dateTime('2013-05-09T05:34:00-04:00')