Custom Start Date for Calculating Earnings

I think it would be very helpful to have the option to choose the specific day from which earnings are calculated, either for a month or a week. For example, I get paid on the last Friday of each month. If my earnings are calculated starting from the 1st of the month, any work done after the last Friday until the 1st of the following month doesn’t get included in the current month’s earnings. This forces me to manually adjust the calculations every month by adding the missing days and removing the days after the last Friday, which will be paid in the next month. Being able to customize the start date would make this much easier.