The export of the event calendar data to ICS works fine. The only issue is on March 13th the time shifts 1 hour ahead so while on the site it reads correctly say 9 AM the imported data to outlook or any calendar states it is 10 AM for the event.
I have checked all calendar options and this appears as though the issue is with the export not keeping the daylight savings time correctly.
you can replicate this by going to the site and exporting March to your calendar.
Try changing the global timezone within your WordPress settings to be the UTC version rather than the local city based version. This should help since, for example, UTC-6 will always be UTC-6 while the city based timezones could be UTC-6 or UTC-5 depending on daylight savings.
If I change this to -6 UTC which is what the current time zone is on the 13 it then show 8:00 AM and not 9:00 AM so it is the opposite from the Chicago timezone.