Probably just me, but I'm not sure what it is that you need.
Sure you saw this, but if you want the number of days SQL_TSI_DAY as the first parameter.
I want this date on my calculated field:
Start Time: 4/5/2017 10:11 AM
End Time: 4/11/2017 11:20 AM
Time_Spent; 6 days 1 hour 9 min.
Thanks in advance!!