To duplicate a single day's schedule you do one day at a time, either forward or back on the calendar.
When duplicating a job schedule for a single day the trick is to enter the date of the day/job/schedule you wish to duplicate for a single day in the 1st date slot and in the 2nd date slot enter the date to which you want to copy it. Click Dupe and voilà!
This screen points to a schedule on the 14th to be duplicated to the 28th. Click the Dupe button to get started.
This screen points to the five steps to duplicating a single day schedule. Click this Dupe button to finish.
Verify the schedule by clicking on the day and reading the display in the lower pane.