Hi Amber,
I just went into Applied Systems' subscription, confirmed that my user time preference was set to Central time (Chicago) and wasn't able to reproduce this issue.
Here's what I see when I set up a test event:
Here's what I see when I try to schedule a test campaign (run once, as well as schedule recurrence):
The time zone for scheduling events/campaigns is based on your personal time zone preference (not the time zone setting for the Marketo instance). Can you please send a few more details/screenshots?
Thanks,
Ei-Mang