Late to the question, but was wondering the same thing while testing out the topic timers for an important announcement of awards being given out by our organization and I do not want to publish it at the wrong time.
It might help the less discourse savvy (like me) if the interface indicated the time was local. But to be sure I created a test at 10am local, set a custom date (today) and time (noon), and the interface did indicate that it would be published 2 hours from now.
A time zone reference (like the Insert date/time in the editor) is handy for us as we are an international organization.