I don't know about "easy".
Now that you have the list of objects that are in your schedule, you could return the min(start time) and max(end time) for a given day from the statistics table for that list of objects. Those statistics are stored in the AH table. Column ah_timestamp2 contains the start time, and column ah_timestamp3 contains the end time, both stored in GMT. The SQL could compute the difference between the min() and max(), thus giving you "turnaround time" for that day.
EDIT:
MatthiasSchelp has provided the appropriate query for returning the litteral "turnaround time" for a schedule object. I was thinking your requirement was more like "how long does it take for the objects in the schedule to run". I suspect Matthias's SQL is what you really want?