Typically, you should choose a timesheet period that matches your payroll and/or billing cycle, be it weekly, biweekly, semi-monthly or monthly.
Weekly timesheet periods promote timely entry of timesheet data, therefore some organizations use a weekly timesheet even if it doesn't correspond to their payroll or billing periods.
Weekly end-of-month timesheet periods can be used in organizations with monthly payroll or billing cycles who would like timesheets to be completed weekly. With this type of timesheet period, the first and last week of each month is flexed (shortened or lengthened) so that a period ends on the last day of each month, and all timesheet periods include at least 4 days. Timesheet period flexing ensures payroll administrators will receive data for the end of the month without having to wait for a future timesheet to be submitted.
Manual timesheets are typically only a temporary measure, used during time spans when your organization will not be following a standard timesheet period schedule. For example, if you are changing your payroll or billing cycle, you may need to use a manual timesheet as a bridge between regularly scheduled timesheet periods.
For more information on each type of timesheet period, and on how to set them up, refer to Defining Timesheet Periods in Replicon's online help.