Calendars events showing multiple times since time change

I have a macbook pro running on 26.? And an iphone running on 26.7.1. Since the time change 4 days ago, events that I had previously entered on my calendar are showing the wrong time by 1 hour and the correct time immediately after that with (CDT) following the correct time. Yet a third time is shown on the summary on the calendar itself & in the notification for the event that is 3 hours off! The time shown on the event on my iphone is correct. What the heck is going on? I have never had any glitches with a time change before.