Hi anvilring,
Thanks for posting your question here. If you would like to change the post time of an item you have scheduled but has not posted yet, you can do so from your Scheduled Listings page, which you can reach by mousing over the "Listings" tab within your account and selecting the "Scheduled" option.
From there, just check the box next to the desired scheduled listing and click the "Edit Post Time" button and you will be presented with an interface you can use to change the time at which the item is scheduled to post.
I hope this helps!
-Mike
