How Many Weeks In A Month For Payroll Calculations?

There are usually two different types of payrolls.  The ones that are biweekly, which means, they take hours worked in a two week period and pay you accordingly every two weeks.  Then there is the Bi Monthly, which I don't care for, were you are given a base salary for a month and divided in two.  I find this method to benefit the employer and not the employee.  Depends on if you are working hourly or weekly, as in weekly salary.