Scenario:
Sometimes it is necessary to find out the exact number of hours which a user is supposed to work in a period ( week, month, year etc). In this scenarios, you can go ahead and enable Work Week Hours (Period)  to find out the number of hours. Work Week Hours ( Period)  is available for selection in Timesheet Detail report.Application would automatically reduce weekly days off and the holidays falling in the period to calculate the exact number of work hours in the period.

Work Day Hours = (Total days in period – Weekly days off – holidays) * Hours Per Day

For example a user created in Web Timesheet with following options,
Timesheet Period : Weekly.
Weekly Dayoff     : Saturday and Sunday.
Hours Per day     :  8  Hours.
Holiday Calendar : Holidays for United States.

For a Timesheet period starting  20/11/2011 and ending on 26/11/2011 , the work days  hours (period) would be calculated to 32 hours as there are 7 days in the period – 2 weekly days off – Holiday ( 24/11/2011 – Thanks Giving Holiday) multiplied with number of hours per day.
Work day hours do not take into consideration the start date of the user, but sometimes it is required to customize work day hours to find exact work days hours in relation to the start date of the user.

Resolution:
Create a custom column in Timesheet Detail report with following code to calculate the Work Day hours with relation to the start date of the user.

if(daydiff(TimesheetStartDate,UserStartDate)>0,IF((MOD((daydiff((date(1990,1,7)),TimesheetStartDate)),7))!=0,(TotalPeriodWorkDayHours – ((daydiff(TimesheetStartDate,UserStartDate)))*HoursPerDay),(TotalPeriodWorkDayHours – ((daydiff(TimesheetStartDate,UserStartDate))-1)*HoursPerDay)),TotalPeriodWorkDayHours)