I have the same, or similar, experience. This plugin interferes with my My Calendar plugin and changes all the times.
So, a temporary workaround is to set the timezone for the ultimate auction plugin to the London timezone (even though I live in Sweden). This will adjust the times in the calendar to the correct start- and end time.
However, this will also have an impact on the start- and end times when adding a new auction. If I set the end time to 1 PM (13:00) – now it’s 12:24 – it will say that the auction ends in 1 hr and 35 minutes.
I’m not really sure what’s my best option here.