There are below steps for configure attendance period falling in two months:
1.Navigate to: Control Panel->Setting-> Payroll
2. Newly Page will be Open.
3. Enable this option of "Run payroll for attendance dates falling in two months" and you will see the system is automatically unlock the option of "LOP Start Date" and You have to select Start date and Select Month.
Note: if you want to keen 22nd to 21st of your company Attendance Period then Select Start date is 22 and Select month is "Previous Month"
4. Click on "Update Details" for Update above setup.