Marketo has two options for setting timezones: one is for user-level timezone settings (Marketo Admin > My Account > Location Settings > Time Zone) and the second is for the entire instance-level timezone setting (Marketo Admin > Location > Default Location Settings > Time Zone). With the former, the instance time zone doesn't change, only you see the times everywhere in the instance (with a few exceptions in reports) as per the timezone set, and with the latter, you can update the time for the entire instance, and users w/o any timezone set get changed to this instance timezone too. However, I don't think you can just change the timezones selectively for a few campaigns, it applies at the user/instance level across all the modules.
