iPhone Today View for Apple calendar Whats Up Next showing wrong time
I suspect there's a time zone issue if you're travelling a lot between time zones. 

Does it help to go into the Calendar settings in iOS and set Time Zone Override? I'm not sure how it works, but worth having a look at it. Additionally, you can also set the time zone for individual events for particular time zones. 

I've attached a screenshot of the Time Zone Override screen in the Calendar settings on iOS.