Hi mzchristy,
One you have scheduled your listings to post at a specific time, the only way to change the scheduled posting times from the "Scheduled Listings" page would be to edit them one by one, as you have described.
However, a more efficient way to accomplish the same thing may be to cancel them in bulk from your "Scheduled Listings" page, and then go back to your "Saved Listings" page and reschedule them in bulk.
Any additional questions or concerns? Please file a support request using the appropriate link on our help page: http://www.auctiva.com/free-auction-software-help/help.aspx
-Mike