I have many events which are recurring. When I set these events, I use the local timezone (ET). I have noticed that when I open a single occurrence (rather than the recurring series), the timezone is set to Atlantic Time and grayed out. So the event shows as an hour later. The recurring series is set to Eastern Time and shows at the correct time.

I can't figure out how to get access to the timezone box on the single occurrence. While I can work around this by using Atlantic Time in the single occurrence, I find it annoying and would like to find a fix.