As far as I can tell, the publishing/scheduling behavior of the plugin is locked to work on GMT time, rather than using the configured timezone. This is confusing because it isn't implemented consistently across the interface. (While consistency would be better, I'd ideally prefer that the timezone be respected.)
As example, at the top of the Auto-Schedule screen for me right now, is:
Now: 2012-05-25 15:11:10
Next: 2012-05-25 15:10:00
We should be open to publish now
This is correct for me at GMT -5 (DST).
Now, if I set my end time to 16:00, which is obviously in the future, that information updates to saying the system should not be open to publish, thought it should be. (If the timezones matched.) I have to add a gap exceeding my GMT offset before the system reverts to "open" status.
I see nothing mentioning this discrepancy, so have to assume it's unintended, but if so it should at least be documented. The nearest is that the start and end times are labeled as "military time" but that only implies 24hr format, not that it's UTC/GMT.