If you're adding an event that crosses time zones (like a flight, train, or cruise) you may need to set different different time zones for the start and end of the itinerary event.
And sometimes when you import your itinerary from third-party services like TripIt, Planapple may not be able to figure out the correct time zone, and may show the generic "UTC" time for the event.
You can change individual event time zones from Planapple's Itinerary.
For an event with a single start and end timezone, you can just click on the timezone abbreviation in the itinerary, and choose the new one. Here's an example changing the time for a dinner reservation from the US-Pacific ("PDT") timezone to Hawaii time ("HST"):
For an event with different start and end timezones, you can use the Edit Schedule dialog. Here's an example setting the start and end timezones for a flight:
(If you don't see the start and end times for the item, click "More Options" at the top right of the Edit Schedule dialog.)