You can filter the results by server (and then also involved nation). Some examples:

• All port battles on Antigua: http://potbs.armeagle.nl/portbattleschedule.php?server=Antigua
• All port battles on Antigua involving British: http://potbs.armeagle.nl/portbattleschedule.php?server=Antigua&nation=British
• All port battle on Antigua not involving British: http://potbs.armeagle.nl/portbattleschedule.php?server=Antigua¬nation=British

Now that all might not make much sense. But I received a request to publish this data as an iCalendar feed. And I thought it should be working, but Google Calendar doesn't seem to accept the feed yet.

Feel free to try it out (in other software) though. The base url is http://potbs.armeagle.nl/portbattleschedule-ical.php and it accepts the same parameters as this page. And that's why the in- and exclusive filtering of a nation is for. So that you can color them differently.

Make sure your program doesn't look for updates too often. Once per day should suffice usually. But please don't go above four times per day.