Hi Jonathan.
Unfortunately, there’s a substantial bug where version 4.2.4 of our iCal Importer plugin is setting all the imported events to have the same start time. You might try downgrading to version 4.2.3 and see if this helps with your issue.
If this is what you’re experiencing, I’ll mark this ticket as Pending Fix, which means this thread should receive a reply once the applicable fix has been released. I cannot guarantee when it will be fixed as it’s in the development team’s hands now. They need to assign it, code it, test it, and schedule it for release.
I apologize for this issue and appreciate your understanding and patience.