Port Battle Schedule (UTC timestamps)
Antigua Round: 44 State: Active Time Map
Santiago Pirate (2728)  attacking  France (575)Feb 05 19:00 (7h21m)list of maps *
Port-de-Paix Pirate (3833)  attacking  France (3945)Feb 05 20:00 (8h21m)list of maps *
Nassau Pirate (15868)  attacking  Spain (1477)Feb 05 21:00 (9h21m)list of maps *
Turtling Bay Britain (3665)  attacking  France (557)Feb 05 22:00 (10h21m)list of maps *
Port St. Joe Spain (612)  attacking  France (781)Feb 05 23:00 (11h21m)list of maps *
Puerto Cabezas France (224)  attacking  Britain (2669)Feb 06 19:00 (31h21m)list of maps *
Irish Point Britain (830)  attacking  France (512)Feb 06 20:00 (32h21m)list of maps *
Roseau Spain (0)  attacking  France (513)Feb 06 21:00 (33h21m)list of maps *
Roberts Round: 31 State: Active Time Map
Caracas Pirate (7988)  attacking  France (2597)Feb 05 12:00 (21m)list of maps *
West End Pirate (8289)  attacking  France (7255)Feb 05 13:00 (1h21m)list of maps *
Santiago Pirate (9081)  attacking  Spain (3537)Feb 05 14:00 (2h21m)list of maps *
Testbed Round: 5 State: Active Time Map

You can filter the results by server (and then also involved nation) by adding parameters to the URL; some examples:

Now that all might not make much sense. But I received a request to publish this data as an iCalendar feed. I think it works with most RSS readers/calendars. If it doesn't work for you, let me know. Feel free to try it out, 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.

Please make sure your program doesn't look for updates too often. Once per day should be enough.