Determines whether a given date/time is in summer-time (daylight savings time).

in-summer-time($date as xs:dateTime, $region as xs:string) ➔ xs:boolean





The input date/time




The country code or Olson timezone name




Notes on the Saxon implementation

Available since Saxon 9.1.


The $region argument may either be an ISO two-letter country code (for example de or es), or an Olson timezone name (such as America/New_York or Europe/Lisbon). The function returns true if the given date/time is in summer time (daylight savings time) in that country or timezone, as far as can be determined from the Java timezone database. If the information is not available the function either returns false or an empty sequence.

If a country code is specified for a country that spans different timezones with different daylight savings rules (for example, the US), then one timezone in that country is chosen arbitrarily.

For reliable results, the supplied date/time should include a timezone. This does not need to correspond to the timezone named in the second argument; it is there purely to ensure that $date represents a single point in time unambiguously.