SUMMARY :
  To calculate the 'Number of Days Worked' by an employee in the organization based on the User Defined Field selection in Timesheet.

RESOLUTION :
  Replicon by default offers to have one 'Hours Per Day' option in the User Profile. But in a situation where people work different number of hours per day based on the location they are working, a simple solution is suggested.

  For example : If a person has to work 7.5 Hours per Day when he is in Location I and 12 Hours Per Day if he is in Location II.
A Used Defined Field at Timesheet Row Level can be created by the name 'Location'. Let this be of drop-down type with Location I and Location II as the option (we can set Location I as Default if that is the place where majority of the people will work).
Now in a report (Timesheet Detail Report), we can create a custom column that will have the given formula :

     If(location='Off-Shore',(TotalHours/12),(TotalHours/HoursPerDay))

                 where TotalHours = Total hours worked for that period
                       HoursPerDay = hours per day set in the User Profile