Stand alone definition:
=======================
<extcalendar>
  <noworkday year="*" week="*" day="1" comment="Sunday"/>
  <noworkday year="*" week="*" day="7" comment="Saturday"/>
</extcalendar>

...with reference:
==================
<extcalendar extends="westerneurope">
  <noworkday year="*" month="12" day="24" comment="Christmas"/>
  <noworkday year="*" month="12" day="25" comment="Christmas"/>
  <noworkday year="*" month="12" day="26" comment="Christmas"/>
  <noworkday year="*" month="12" day="31" comment="End of Year"/>
</extcalendar>
